|“||If there are those that will hurt my important people then I will definitely defeat them even if they may be a God.||”|
– Issei's new determination upon becoming a High-class Devil, Volume 22, Life 2 And thus, to a High-class Devil
Issei Hyoudou is the main male protagonist of High School DxD. He is a third-year high school student at Kuoh Academy in Class 3-B and a member of the school's "Perverted Trio", a trio of the most perverted men in the entire student body.
He is a member of the Occult Research Club and the Pawn of Rias Gremory's Peerage. After the Evil Dragon War, he was promoted to the rank of a High-Class Devil, becoming the King of his own independent peerage, and is one step closer to fufilling his dream owning a harem and becoming a "Harem King".
Due to his possession of the Longinus; the Boosted Gear, which hosts the Welsh Dragon; Ddraig, Issei is the direct rival of Vali Lucifer, who is the host of the Vanishing Dragon; Albion, who is Ddraig's archrival.
Issei is a high school student of average height with short spiky brown hair, with two short locks of hair behind his head, and light brown eyes. Following his training with Tannin in Volume 5, he gained a more muscular and toned build.
While he has worn various outfits throughout the series, his most commonly worn outfit is the Kuoh Academy boys' school uniform, which consists of a blazer (more commonly black, although in other media is shown with a tinge of purple or grey, with white accents) over a white, long-sleeved dress shirt with black highlights with a black ribbon on the collar, matching black pants, and brown dress shoes. However, Issei's uniform differs in the fact that he wears a red T-shirt underneath his open dress shirt and blazer, and wears blue and white sneakers in place of dress shoes.
From the end of Volume 2 to the beginning of Volume 12, Issei's left arm was transformed into that of a Dragon. In order for it to appear human, a ritual would be performed where Rias or Akeno would suck the power of the Dragon out of it, allowing it to appear human for a few days. After gaining a new body in Volume 12 through the combined efforts of Great Red and Ophis, he is now able to freely transform any part of his body into that of a Dragon.
He has been said to show manly expressions by his paternal grandmother. Issei's height is 170 cm (5 feet 7 inches) and body weight is 62→65 kg (137→140 lbs.).
Issei is initially shown to be ignorant, self-centered, arrogant, and his ongoing perverted nature, often to make lecherous fantasies, and utterly obsessed with women's breasts and having his own harem. This has caused him to be instantly labeled as a pervert among the girls of Kuoh Academy and has gained him notoriety for being one of the members of Kuoh Academy's Perverted Trio.
Despite his pervertedness, Issei is courageous, selfless and unwaveringly determined to protect those who are important to him, despite almost dying by the hands of his opponents. Having great kindness, Issei is also very caring, "putting his nose into other people's business" as he helped Yuuto Kiba, Koneko Toujou, and Akeno Himejima overcome their fears and hatred of their mournful past. Due to this, he gained strong friendship from his comrades and affection from most girls of the Occult Research Club and a strong sense of friendship with higher-up Devils like Rias' family; they have told him to use the same titles for them as Rias (Father, Mother, Brother, etc.), yet he still remains the same.
He has a habit as mentioned by his mother of not forgiving himself if he does something wrong: always saying sorry if said thing is mentioned, and showing an expression of pain and regret. He is also fiercely loyal to his comrades and is always willing to stand up for them. Issei's kindness also have a positive influence on others including former enemies. When Issei suggested to Cao Cao to use his True Longinus to help and protect people, Cao Cao acknowledged had he and Siegfried met and befriend Issei earlier, they would not have ended up becoming terrorists in the Khaos Brigade. Another sign of his kind nature is that despite wanting to lose his virginity, Issei refuses to take advantage of women when they are upset, even if they themselves are willing to. This happened when Akeno appeared in front of him naked and wanted to have sex to forget about her sad past and her father. However, Issei refused, knowing it will just hurt her more, and put her clothes back on and hugged her to comfort her.
After his murder by Raynare, Issei had developed a fear of admitting his feelings to the girls, as he thought it would cause them to turn their backs on him. This would also cause him to become oblivious to the feelings of the girls around him (save for Rias after his confession), often believing they are simply teasing him. He acknowledged that this would never happen, but it was still an intense fear. It is also why he was so insistent on trying to lose his virginity, as he believed that no woman would ever want to be in a true relationship with him and that him having sex was the best he could hope to achieve as a sense of relief. Despite that, even when the girls of the Occult Research Club such as Akeno or Xenovia propositioned him into making love to them, Issei would always initially hold himself back, as he would sometimes look at them with a frightened gaze, a fact which Akeno, Asia and Koneko later noticed. In Volume 10, his fears were finally brought to attention when Akeno, Asia, and Koneko confronted him alone and helped him by getting him to admit his feelings and assuring him that they would always love him and so would Rias. This inspired him to finally confesses his love for her which she reciprocated, effectively helping Issei move past his fears. Even with the knowledge that the girls do have romantic affection for him, he still has problems acknowledging some of their ongoing rivalries, an example being who gets to sit on his lap.
In reality, Issei has an innocent side; he is a boy who yearns for love and a true relationship, a side which he only shows to women who can see past his perverted exterior and love him for who he is and who he, in turn, has affections for. He shows this side to the girls of the Occult Research Club, for instance on his date with Akeno or when Rias takes him out on dates.
Initially, after reincarnating as a devil, he set about his desire for a harem as his initial goal, by having his peerage become his harem. After the Rating Game against Sona and Saji, he slightly changed the goal to having a harem peerage that wouldn't lose to anyone. Among his other goals include competing in Rating Games and making Rias the Champion of the Rating Games by becoming the "Ultimate Pawn" alongside Kiba, who promised to become the "Ultimate Knight" with him and his desire to become the Champion of the Rating Games himself after he obtains his own peerage. He is also deeply invested in his rivalry with Vali Lucifer, his Heavenly Dragon counterpart, as Issei promised to get stronger and defeat him, with the both of them reaffirming their promise to fight each other some day multiple times during the series and Vali suggesting that Issei create his own team like Vali which is different from his peerage. Their rivalry would heat up after the both of them enter the Azazel Cup, with Issei creating his own team, "Team Red Dragon Emperor of the Blazing Truth", to try to win the Cup and defeat Vali during the tournament. After the two of them passed the preliminary rounds, the two expressed their desire to continue their initial fight as the both of them promised not to lose until they meet each other in the Cup.
As revealed by Shiva, Issei has a deep desire for peace which is further strengthened by him being the "child" of Great Red and Ophis, as Issei seems incapable of realizing his dream of becoming a Harem King until he obtains peace with his own hands. Due to experiencing intense fights in which he nearly died, Issei affirms his desire to create a world without war and protect his companions even if his enemy is a God.
While initially shown to be unable to understand the appeal of fighting, Shiva reveals that Issei has developed fondness of fighting strong opponents with strong beliefs, with Issei himself confirming that he has come to like defeating strong opponents as equally as groping female breasts. While Issei is shown to like battling strong opponents, at first he was unable to truly "enjoy" a fight (except his match with Sairaorg) due them mostly being life-threatening fights. This began to change after his match with Dulio, as he realized that competing in the Azazel Cup is mostly sport rather than a serious fight.
Issei is shown to admire strong individuals who have strong beliefs and convictions, seeing them as targets for him to catch up to. He is shown to admire Sairaorg Bael, after witnessing his strength and noble splendor and that respect intensified after learning that Sairaorg was talentless like him, as he noted their similar fighting styles. Due to his interest in Rating Games, he has developed a admiration towards Diehauser Belial and Rudiger Rosenkreutz, due to them being the Top 10 Rating Game players, with Issei especially admiring Rudiger Rosenkreutz; due to him being a reincarnated devil like him. As Dragon, he is shown to admire Tannin, admiring his strength and his desire to help other Dragon as Issei considers him the true Dragon King due to his splendor, and Crom Cruach, due to his overwhelming power and his pride as dragon. While he was initially exasperated and annoyed by Fafnir and his panties fetish, Issei is shown to have developed a respect for him after he witnessed Fafnir's willpower and determination to protect Asia from Rizevim.
Issei is noted be be a very friendly person, able to become friends with anyone. Azazel stated that he has the ability to win over the trust of others easily and doesn't discriminate against anyone as others can feel at ease with him due to him not resenting anyone, with Azazel calling that ability a talent of Issei's. Issei's ability to attract companions, allies and enemies is further enhanced by him being the Red Dragon Emperor. According to Cao Cao, despite Issei's lack of natural talent and demonic power, Issei's ability to attract others by holding dragon powers is top notch compared to previous Red Dragon Emperors, as Cao Cao believes that Issei will become the most dangerous Red Dragon Emperor. His ability to obtain the trust of other is so great that the residual memories of the past Red Dragon Emperors sacrificed themselves to protect him from Samael's curse. After coming back from the dead with by using Great Red and Ophis' power, Cao Cao commented that Issei's power to attract the strong is scary due to it attracting powerful beings like the Dragon Gods to aid him. According to Azazel, Issei makes a lot of irregular phenomena occur, for instance; a lot of Sacred Gear possessors near Issei were able to awaken irregular Balance Breakers (such as Yuuto, Gasper and Saji). Ophis stated that Issei is as strong as the number of companions he has. According to Azazel, Issei has the natural ability to make supernatural girls fall in love with him, while Millarca Vordenburg stated that most of the men who meet Issei become fascinated with him.
While initially being confused by his popularity among the devil children due to Oppai Dragon, Issei eventually embraced the role of being the Oppai Dragon and began acting as a hero for the children as was demonstrated in Volume 10, where he carried the wishes of child fans during his match with Sairaorg Bael, promising to defeat him for the sake of Rias and the children who believed in him. Issei has placed the his desire to protect the children of the Underworld and of the other factions as one of his goals as seen when he defeated various foes who threatened the children and their dreams such as Shalba Beelzebub, Grendel, and Erebus. In fact, due to Shalba's insanity and him promising to kill the children of the Underworld for rejecting him as a Satan, Issei killed him to stop his malice from reaching the children.
In battle, Issei is sometimes very stubborn, and due to his emotions, he often charges ahead towards his enemies without a second thought whenever his comrades are insulted, treated badly, or easily defeated. Azazel has stated that it is one of Issei's bad habits. Lately, he has started to become more tactical in his battles, using technique-type strategies to defeat opponents, as shown when he used the abilities of the Wyverns in a unique way to defeat Euclid.
Issei also displays strong moral principles, as seen when he initially refused to actually kill his enemies. Even after killing Shalba Beelzebub, Issei still rarely ever kills his enemies and prefers to either let others do so or simply let them face arrest. While Issei can carry grudges, he is not above forgiving his enemies and becoming friends with them due to his kindness, as seen with Riser, Kuroka, Vali and Cao Cao.
Before Issei's birth, his mother became pregnant twice, but the pregnancies ended in miscarriages. So when Issei's mother got pregnant for the third time, his father had paced back and forth in front of a Shinto shrine honestly wishing that this time they would succeed. When the newborn was finally born he was named Issei, meaning "honesty", for his father's honest prayers.
He is a childhood friend of Irina Shidou and they would always play together back when she still lived in the neighborhood, although he thought she was a boy at the time as he vaguely remembers her. A few times Issei was invited to go to church with her family. On occasions they would stay over at each other's houses, one of these visits when Issei slept over at Irina's, she kissed him while he was sleeping. Eventually, Irina moved to England due to her father's job.
Sometime during his childhood, Issei met an old man who told him and other children stories about breasts, which eventually led to Issei's fascination with them and his perverted tendencies.
He attended the same middle school with Matsuda and Motohama and the three of them started attending Kuoh Academy one year before the story, and have come to be known as the Perverted Trio to just about the entire school.
Powers & Abilities
Demonic Power: Issei has all the powers common to Devils, including the power to cast spells, but his demonic powers were at first lower than a child's, leaving him unable to travel using magic circles. However, this changed after training with Tannin granting him sufficient demonic power to do so. His demonic powers can be enhanced through promoting to either Bishop or Queen. In Volume 14, Issei can summon Ryuuteimaru. In Volume 25, he can use magic communication circles; and in True Volume 2, he can create a teleportation magic circle.
- Promotion (プロモーション, Promōshon): Being a Pawn, Issei can use the promotion to temporarily gain the traits of a Queen, Rook, Knight or Bishop. In Volume 8, after Ajuka Beelzebub rewrote Issei's Evil Pieces, Issei can now use Promotion anytime and anywhere without the King's permission.
- Dragon Shot (魔力弾, Doragon Shotto): One of Issei's signature moves. Issei fires a beam of energy by concentrating his demonic power. This move is usually used in tandem with the Boosted Gear to increase its destructive powers. He has also developed a small scale Dragon Shot that is meant for knocking out humans while fending off the members of the Hero Faction who are humans. In his Balance Breaker state, he can fire his Dragon Shot without increasing its destructive power. After his fight with Sirzechs, being inspired by the way he uses his Power of Destruction, Issei starts working on how to redirect his Dragon Shot by moving them in different directions, first using it in Volume 9 against Cao Cao and again in Volume 12 during his battle against Jabberwocky.
- Dress Break (洋服崩壊, Doresu Bureiku): The second of Issei's signature moves which he uses mainly against females. This move allows Issei to "strip" women by first coming in contact with them, concentrating his demonic power, then snapping his fingers to activate one of two effects.
- Ver. B (Body): This move is used to "strip" women by destroying their clothes and/or armor.
- Ver. A (Astral): This move is used to "strip" women by destroying the effects of spells or abilities that have been used against them.
- Pailingual (乳語翻訳, Pairingaru): Issei's third signature move. Pailingual gives him the ability to talk to the breasts of all females. It is a helpful technique as it helps Issei learn his opponents' plans and strategies by asking their breasts; however, due to complaints from female members from other peerages, Rias banned Issei from using this technique in Rating Games. This move, however, has a weakness which was shown in the Rating Game between Sairaorg when his Bishop Coriana Andrealphus started to strip in front of Issei, and instead of telling him battle plans her breast told him what she was going to strip next thus hindering Pailingual. In True Vol 1, Issei can combine Penetrate with Pailingual to talk to the breasts of powerful beings and in his Diabolos Dragon form, Pailingual pink space covered the whole island.
- Pai-Phone (乳語電話, Paifon): A variant of Pailingual, using women's breasts Issei is able to communicate through breasts to other women's breasts.
- Flame Blaze (火の息, Fureimu Bureizu): Following his training with Tannin, Issei learned how to use Dragon Flames through using Boosted Gear. He first inhales air filling his lungs, then produces a small flame in his stomach with his demonic power; then Boost and Transfer to enhance the flames within his stomach and he breathes out dragon flames from out his mouth toward his opponent. Because of the training, Issei has also developed a high degree of resistance to fire attacks, so that only the most powerful flames, such as those of a Dragon or the Phenex Clan, can injure him. He's also shown to widen the range of his dragon flames that can engulf the whole sky as shown in his battle against Cao Cao in Volume 12.
- Castling (キャスリング, Kyasuringu): Upon becoming King of his own peerage, Issei gained the ability to use this move, which allows him to swap locations with one of his Rooks. He first used it in his match with Baraqiel to escape a sealing barrier by switching with Rossweisse.
- Nyuutron Beam Cannon (超乳波動砲, Niyuutoron Bīmu Kyanon): Issei's fourth signature move, which is the end result of assistance from his grandfather and Guanyin, letting him attach his Scale Mail's tail onto a woman's breast to convert their "Breast Power" into demonic power with their bust size displayed on his gauntlet's jewel and determines how powerful the blast will be. By using Rossweisse's breasts, which are 96, he could launch an enormous pink blast comparable to Infinity Blaster, defeating the Strongest Grim Reaper, Thanatos.
Immense Strength: At the beginning of the series, Issei's strength was considered below average compared to others. After his training with Rias and the others in the mountains, Issei using his Boosted Gear as shown that he could fight on par with Riser's servants. His training with Tannin has enhanced his strength to where he could erase a mountain after using Scale Mail and outclass Diodora who was empowered using Ophis' snake. It is also stated various times in the light novel that his power is equal to that of an Ultimate-Class Devil. Azazel has also stated that among the Young Devils, Sairaorg Bael; the former Strongest Young Devil is the only one able to fight against Issei head-on. After daily training with Kiba, and with the assistance of Sun Wukong himself his strength further enhanced to the point that he can fight against Rizevim Lucifer, a Super Devil. He later showed to be able to fight against Apophis, one of the Three Strongest Evil Dragons, who achieved Heavenly Dragon-Class powers and defeating him using both Infinity Blaster and Longinus Smasher. In Volume 22, Baraqiel stated he cannot defeat Issei in terms of raw power. In Volume 23, Issei was able to fight on par with Dulio Gesualdo; who is known as the Strongest Brave Saint and Trump Card of Heaven. In Volume 24, Issei was able to keep up with Thanatos; who is known as The Strongest Grim Reaper. In Volume 25, Issei can fight on par with Vidar in his Ragnarök Earth Berserk using Pseudo-Diabolos Dragon. In True Volume 1, Ddraig stated that Issei's strength in his Crimson Armor is equal to a Satan-class Devil and that in his Pseudo-Diabolos Dragon, he can fight against Super Devils. In True Volume 2, Issei was able to defeat Rias in her Forbidden Invade Balor the Princess form, by using a combination of Infinity Blaster and Nyuutron Beam Cannon at the same time. In True Volume 3, Issei was able to defeat Erebus; the Primordial Greek God of Darkness. He later defeated Tartarus; the Primordial Greek God of the Abyss by using AxA. His dragonic aura in his DxD form is powerful enough to blow up to 100 High-class Devils in a single blow. In True Volume 4, after unlocking True Dragon Deification he easily overpowered and defeat Angra Mainyu and then Hades with the help Vali and the rest of Team DxD. He along with Vali were acknowledged by Ajuka as the new Super Devils.
Immense Durability: Issei was originally very weak and vulnerable, easily hurt by the simplest attack. Through the use of Promotion, he can increase his defense. After his training with Tannin, where he was forced to survive Tannin's continuous assault, Issei's durability greatly improves, along with his daily training further enhanced his durability to the point where his body could withstand continuous usage of the Boosted Gear which he couldn't do so in the beginning. In fact, Issei's durability has been proven several times against opponents like Sairaorg Bael, Cao Cao, Grendel, and many others. In Volume 22, Issei can endure Baraqiel's Holy Lightning and continuing to fight despite the intense pain. In Volume 25, Issei can withstand Vidar's attacks even when he is wearing his Ragnarök Earth Berserk armor and even his signature move; Fimbulvetr Shot, the impact of which sent Issei crashing onto artificial Yggdrasil.
Immense Speed: Through the use of Promotion, Issei can increase his speed. In his Balance Breaker state, he can use the booster to further increase his speed. In Volume 20, in his Diabolos Dragon form, he was able to appear in front of Rizevim before he can react. He was able to keep up with Vidar in his Ragnarök Earth Berserk. In his Pseudo-Diabolos Dragon form, he was easily able to keep up with Yuuto Kiba, who is famous for his exceptional speed, until Kiba revealed his Drag Knight Boosters.
Immense Stamina: Issei originally possesses average stamina. After being reincarnated into a Devil along with his daily training with Rias, Issei obtains more stamina to use the Boosted Gear. Following his training with Tannin in the Underworld, Issei obtains even more stamina, that he could use when in Balance Breaker. He eventually obtains enough stamina to activate his Scale Mail without a countdown. In Volume 23, he was able to keep fighting at his best throughout the whole two-hour Rampage Ball Rating Game.
Dragonification (龍化, Ryū-ka): Having sacrificed his left arm to Ddraig, having it transformed into a dragon's arm in Volume 2, Issei's left arm became immune to damage taken from touching Holy objects. In Volume 14, due to his new body being created from Great Red's flesh, Issei can now turn any part of himself into that of a dragon by focusing his thoughts on that specific part as he turned his right arm into a dragon to combat three Magicians to sent to attack Kuoh Academy letting him break their defensive magic using a single punch. Issei is able to grow Dragon wings from his back. Unfortunately, once the transformation occurs, he is unable to return it to human form, unless he gets the Dragon energy drained from the transformed body part by either Rias or Akeno.
Master Hand-to-hand Combatant: Issei was unskilled in combat at first, but after training with both Koneko and Kiba, he managed to obtain basic hand-to-hand combat skills. He can combine the boosted power from Boosted Gear and dragon aura increases the power of his physical attacks. After training with Tannin, Issei became more skilled in combat, learning how to survive the former Dragon King's assault. In fact, his prowess is shown as he could go toe-to-toe with Sairaorg Bael, a master martial artist in his own right in a fistfight. After daily training with Kiba and even Sun Wukong, he improved his skills to where he could handle the assaults from the likes of even Diehauser Belial and Rizevim Lucifer, who are powerful devils that are skilled in hand-to-hand combat, then overpowered the latter using Diabolos Dragon. In Volume 22, Issei using Cardinal Crimson Promotion is able to fight on par with Baraqiel, who infused both his punches and kicks with Holy Lightning. In Volume 25, Issei in his Pseudo Diabolos Dragon armor went toe-to-toe in his fight with Vidar, who has excellent powerful kicking techniques even when Vidar was being enhanced by the power of his Ragnarök Earth Berserk armor. In True Volume 3, Issei demonstrated his experience and mastery of hand to hand combat when he overwhelmed Gressil, a powerful Satan class Devil at least until the latter's "Resistance" ability started to make him more resilient against Issei's attacks, though Issei still had the advantage.
Skilled Swordsman: Though Issei isn't proficient or talented in swordplay like Kiba or Xenovia, he has learned the basics from Kiba, which has been improved from training sessions. As such, he can wield Ascalon instead as an extension of his Boosted Gear. While not on the level of sword masters such as Kiba, Xenovia or Irina, Issei does have solid skill enough to deflect strikes from Thanatos' scythe using Ascalon, then fought Vidar using both it and Ascalon II. Issei develops a technique to shoot out his swords at his opponent enhanced by using both Boost and Penetrate. In True Volume 2, he could block a strike from Kiba using Ascalon. His skills has allowed him to wield all three Ascalon against Angra Mainyu, even using feints against him before stabbing him with his Tail Blade.
Skilled Tactician: Although he is often outsmarted and considered an idiot, he is proven himself to be a slightly skillful tactician. In Volume 9, he acts as a leader and a tactical fighter, where he uses his brain to fight properly the Hero-Faction. Issei claims that his skills are not that enough, but Kiba mentioned that if it is not for his orders they couldn't fight and defend themselves from the sudden attacks of the Hero Faction. In True Volume 2, Issei demonstrated good tactical knowledge in his fight against Kiba, by exploiting his Transfer to make Kiba lose control of his speed thus negating Kiba's speed advantage. During his fight against Rias, Issei was able to exploit the fact that she was unfamiliar with his Nyuutron Beam Cannon to surprise her during their fight, allowing him to defeat her. Issei is currently learning Rating Game tactics from Ravel.
Survival Skills: Because of his training under Tannin, Issei has developed survival skills.
Stealth: Issei has also learned how to mask his presence from people.
Flight: While Issei still lacks the ability to fly using his Devil wings, Issei being a former Dragon can fly using his Dragon wings.
Boosted Gear (赤龍帝の籠手, Būsuteddo Gia): Issei's Sacred Gear and main weapon. The Boosted Gear is one of the 13 Longinus which holds the spirit of the Welsh Dragon, the Red Dragon Emperor, Ddraig, one of the Heavenly Dragons. It is said to have the power to kill a god when fully mastered. Boosted Gear takes the form of a red gauntlet on the wielder's left hand that has the ability Boost , which doubles the user's power every 10 seconds without limit; and its sub-ability which can Transfer, the multiplied power to a being or object and it can even be focused on certain parts of the user's body such as the eyes for enhanced vision. Issei can use Boosted Gear to strengthen his physical abilities and demonic power. Later, it gained Penetrate to bypass any defensive abilities (including Rizevim's Sacred Gear Canceler) that would otherwise prevent his attacks from landing, however, it does not negate the deactivation of Balance Breaker. Penetrate's effects can also be channeled through any part of the body, such as the eyes, making it capable of seeing through anything, even women's clothing.
- Boosted Gear: Scale Mail (赤龍帝の鎧, Būsuteddo Gia: Sukeiru Meiru): The Balance Breaker of Boosted Gear that creates a Red Dragon Armor and Issei's primary battle form. Issei first activated his imperfect version of Scale Mail in Volume 2, by making a pact with Ddraig by giving his left hand to the latter. During his first battle against Vali, Issei used a bracelet given to him by Azazel which allowed him to use the imperfect version of Scale Mail for less than 15 minutes. Issei completed his Balance Breaker during his fight against Kuroka, poking Rias' breast to trigger the evolution. From this point, Issei can Boost without the 10-second limit and it strengthens his powers and abilities. At the back of his armor, there are two rocket boosters that give a temporary boost of speed and flight. After the activation of the Juggernaut Drive, Issei's Scale Mail gained a pair of retractable Dragon Wings with Pteranodon-like claws that he can use as arms.
- Juggernaut Drive (覇龍, Jagānōto Doraivu): A form unique to the Boosted Gear and Divine Dividing. The Juggernaut Drive temporarily removes the seal placed on the Heavenly Dragons granting the user immense power. The Juggernaut Drive, however, causes the user to lose sanity while having their lives devoured by power. Issei indirectly activates an incomplete version of this form when he thought Asia was killed by Shalba Beelzebub with the negative emotion overpowering him thus triggering the Juggernaut Drive. In this form, Issei's speed is greatly increased to the extent that it can be hard for one's sight to follow. This form is also capable of creating Dragon arms and blades from the gems of the armor. It contains a small cannon within the mouth of the helmet that shoots out a laser beam.
- Longinus Smasher (ロンギヌス・スマッシャー Ronginusu Sumasshā): It is finishing that is the most powerful attack of the Boosted Gear. A launcher appears from the chest of the form that is capable of shooting a powerful energy beam of immense destructive power.
- Illegal Move Triaina (赤龍帝の三叉成駒, Irīgaru Mūbu Toriaina): The Illegal Move Triaina is a specialized technique used by Issei Hyoudou that changes his Scale Mail armor into three different forms based on the Evil Pieces system.
- Welsh Sonic Boost Knight (龍星の騎士, Werushu Sonikku Būsuto Naito): Triaina's Knight form. In this form, Issei possesses enormous speed that far surpasses Sairaorg's speed, but to make full use of it, Issei must shed his excess armor, causing it to become thin to the point where it has low defense, making him vulnerable to powerful attacks.
- Welsh Dragonic Rook (龍剛の戦車, Werushu Doragonikku Rūku): Triaina's Rook Form. In this form, Issei possesses a massive amount of power and defense but has a low body maneuvering speed because of the massive, thickened armor.
- Solid Impact (ソリッドインパクト, Soriddo Inpakuto): It's respected finishing move that delivers a punch that has its power and speed increased by nailing the percussion hammer located at his elbow.
- Welsh Blaster Bishop (龍牙の僧侶, Werushu Burasutā Bishoppu): Triaina's Bishop Form. In this form, Issei possesses an enormous amount of demonic power, which he applies it to the two cannons at the back of his armor.
- Dragon Blaster (ドラゴンブラスター Doragon Burasutā): It's respected finishing move that is a severely boosted equivalent of his Dragon Shot capable of leveling battlefields and briefly warp space-time. The drawbacks to that the amount of time it takes to charge the cannons and stamina lost with each shot.
- Cardinal Crimson Promotion (真紅の赫龍帝, Kādinaru Kurimuzon Puromōshon): The Scale Mail's Queen form that is achieved by gaining the "True Queen". This form changes the color of Issei's Scale Mail armor from red to crimson. Cardinal Crimson Promotion incorporates all three Evil Pieces traits, making it the most balanced and most powerful form of Issei's Scale Mail. In this form, Issei is capable of using enhanced versions of the Illegal Move Triaina's abilities. This form, however, is still unstable and requires mastering the three forms of Illegal Move Triaina to stabilize its powers. In Volume 22, it is revealed that Issei can enter True Queen without having to chant, and due to Diabolos Dragon God mode, its power has been increased.
- Solid Impact Booster (ソリッド・インパクト・ブースター, Soriddo Inpakuto Būsutā): By morphing one of the armor's gauntlets into Welsh Dragonic Rook's, it allows it for an enhanced version of Solid Impact. It can also be used in tandem with Ascalon to deal further damage to Dragons.
- Crimson Blaster (クリムゾンブラスター, Kurimuzon Burasutā): An enhanced version of Welsh Blaster Bishop's "Dragon Blaster" that shoots a powerful beam from the wings of the armor.
- Dividing Wyvern Fairy (白龍皇の妖精達, Dibaidingu Waibān Fearī): Originally taking the form of Dividing Gear (白龍皇の籠手, Dibaidingu Gia), a white gauntlet on Issei's right hand which he obtained in his initial battle against Vali in Volume 4. Issei placed one of the jewels on Vali's armor to him, creating the Dividing Gear which allows him to use Albion's dividing powers. This ability, however, reduces Issei's lifespan and thus was banned by Azazel. In Volume 16, Issei is no longer able to use Dividing Gear after gaining a new ability that allows him to create small white Wyverns from the gems of his armor that can not only Divide but can also Reflect incoming attacks. Unlike the Dividing Gear, It only requires Issei's stamina rather than reducing his lifespan. In Volume 17, Issei manages to change the white Wyverns red at will where they are able to use Ddraig's powers of Boost, Transfer and Penetrate instead. After training with Rias, Issei manages to make use of the red Wyverns to attach themselves on Rias to create her own variation of the Boosted Gear Scale Mail armor called Crimson Extinct Dragonar (深紅の滅殺龍姫, Kurimuzon Ekusutinkuto Doragunā). Issei also made use of the red Wyverns to attach themselves on Xenovia to create her own variation of the Scale Mail armor called Crimson Destruction Dragonar (真紅の破壊龍騎士, Kurimuzon Desutorakushon Doragunā).
- Longinus Smasher (ロンギヌス・スマッシャー, Ronginusu Sumasshā): In Volume 17, Issei gains access to this ability when the Red Wyverns used Boost on him while in this form. An ability initially available to Juggernaut Drive that from the chest appears a launcher that fires a powerfully destructive beam. This, however, leaves strong fatigue on Issei as it drains a lot of his stamina and depending on how one uses it, it can change the environment. Due to its immense power, this ability has a very long recharge period, lasting at least a month.
- Tail Blade (テールブレード, Tēru Burēdo): Using the Ascalon II Prototype, Issei with his tail of his armor can attack with its blade and lengthened the tail towards his enemies at high speed.
- Diabolos Dragon God (龍神化－『D×D』・G－, Diaborosu Doragon Goddo): This form is the result of Issei borrowing Ophis's power. The armor undergoes further change, as its color changes to be both crimson and black and adding a second set of wings. The power this form grants is so great that it overwhelms Rizevim Livan Lucifer's Sacred Gear Canceler, previously thought impossible. Boost has been changed to D∞D as Issei powers up in this form with the ∞ symbol emerging on all of the gems. According to Issei, he was able to use this form because his body was created with Ophis's power and Great Red's flesh. Even so, Issei can only sustain this form for a short period of time, followed by pain that makes death pale in comparison. After the battle against Apophis, Ophis adjusted DxD into DxD G, removing the infinity in it and dubbing the form Pseudo-Dragon Deification (疑似龍神化, Giji no Ryūjin-ka). The form can only be maintained for three minutes at most, with the time limit becoming shorter by attacking or defending to the point it can last only ten seconds. In Volume 23, Issei reveals the ability to perform Partial Pseudo-Dragon Deification (部分龍神化, Bubun Ryūjin-ka) on his left arm, allowing him to use his Dragon God Aura to a lesser extent with less stamina consumption. With this technique, Issei can combine his Dragon God aura into both Solid Impact Booster and Dragon Shot. In Volume 25, after drinking the miracle drug Amrita, Issei can maintain his Pseudo-DxD form for 88 minutes in combat. During his fight with Angra Mainyu, Issei unlocks True-Dragon Deification (真の龍神化, Shin no Ryūjin-ka) which is described as having Devil, Dragon, and God aura. Hades notes that Issei's power in this form is even greater than when he was in Pseudo-DxD.
- Infinity Blaster (インフィニティ・ブラスター, Infiniti Burasutā): A further enhanced version of Crimson Blaster, the wings contain cannons that shoot out a powerful blast of red and black aura that leaves even Rizevim injured to an extent that his body is almost fatally damaged. By using it, DxD G's time limit of three minutes is cut down to ten seconds. After drinking miracle drug Amrita, Issei has overcome this weakness and can maintain his armor after shooting Infinity Blaster.
- Longinus Smasher (ロンギヌス・スマッシャー, Ronginusu Sumasshā): The form is not only capable of this move, but the blast it shoots out has been enhanced with the power of infinity, delivering further damage. It can also be used in tandem with the Infinity Blaster, fusing the two blasts into an even more powerful attack.
- Blazing Inferno of Scorching Flames (燚焱の炎火, Itsu Eki no Enka): An ability that was sealed by the God of the Bible, which Issei managed to unlock upon using his DxD form for the second time in Volume 21. Issei releases a powerful breath of fire that can incinerate anything, flames that never go out once ignited as they continue to burn even after being reduced to ashes and can probably burn the soul until nothing remains. The only existences known to be immune to these flames are Albion, Ophis, and Great Red. Its area of effect can cover an entire island.
- Red Dragon Emperor Ddraig Manifestation (赤龍帝ドライグ顕現, Sekiryūtei Doraigu Kengen): Due to drinking the miracle drug Amrita, Issei gained the ability to summon Ddraig into battle after the  countdown on the right gauntlet reaches zero.
- Dress Break DxD (洋服破壊・龍神式, Doresu Bureiku DīDī): By using his Dragon God aura, Issei can increase his range that halts a female target’s movement, and by strengthening his left hand he can destroy their clothes without even touching them.
- Apocalypse AnswerArms (A×A, Apokaryupusu ansāāmuzu): Issei's AxA form. This form is the result of Issei combining with his familiar Ryuuteimaru, who manifests Great Red's power due to him being Issei's familiar thus allowing him to make use of Great Red's aura in Issei's body. The power of this form is so great that it overwhelms Tartarus, a Primordial God in Greek mythology. It has the power to destroy the entire world with its destructive power. Because of the weapons that were installed in Ryuuteimaru, Issei has gained new abilities in this form. The drawback of this form is that it has an extremely high consumption rate which gives it a short time limit. Furthermore, Ryuuteimaru is unable to move for a few days and Issei himself suffers fatigue for a few days. It is determined that these burdens compared to DxD G are much lighter.
- Revelation Barrier (レベレーション バリアー, Reberēshon Bariā): Creates a stronger barrier around the body and is powerful enough to withstand attacks from gods such as Tartarus.
- Revelation Blade (レベレーション ブレード, Reberēshon Burēdo): With four arms of his Apocalypse AnswerArms form, each of the arms carries a aura blade known as Apocalypse Ascalon (アポカリュプス・アスカロン, Apokaryupusu Asukaron), which can easily cut through anything like Tartarus’ tentacles.
- Revelation All-Range Blaster (レベレーション オールレンジ ブラスター, Reberēshon Ōrurenji Burasutā): Similar to Cardinal Crimson Promotion and Diabolos Dragon God, Apocalypse AnswerArms has many cannons to fire powerful blast of auras that can destroy Tartarus’ magic barriers like paper and destroys almost half of his body, even as Issei held back his power. The blast of destructive energy is so powerful it can alter the environment and is strong enough to destroy the artificial space created Dimension Lost. Issei states that the blast is comparable to several Infinity Blaster's blast attacks combined.
Ascalon (アスカロン, Asukaron): A holy sword given to him by the Archangel Michael, after Ascalon had gone through a number of modification from the current leaders of the Three Factions it could be wielded by Issei, who wasn't a natural-born Holy Sword wielder and dragon host. He was also able to store it inside of his Boosted Gear and the blade emerges from the gauntlet when called. In the anime, it is shown that Issei is able to extend the length of the blade. It is also stated during the Rating Game match against Sona that Ascalon has been imbued with the dragon aura of Ddraig, resulting in an enormous boost in power. Issei learned how to channel the Dragon Slayer power of Ascalon into his punches, allowing him to harm Dragons more easily. Later, Issei managed to combine Ascalon's Dragon Slayer ability with his Crimson Blaster. In Volume 25, Issei is also shown to be able to endow Ascalon with Penetrate and Boost, with the effect staying even after he launches it as a projectile against Vidar.
Ascalon II (アスカロンII, Asukaron II): The second version of Ascalon. A long sword that releases holy aura, but is more of a dragon sword rather than a Holy Sword. Issei keeps this sword within his right gauntlet that was free.
Ascalon II Prototype (アスカロンII プロトタイプ, Asukaron II Purototaipu): The initial prototype model of Ascalon II that Issei used. Due to being created for Issei's use, other people cannot use it which is why the Vatican team that created it left it to him. Although it does not have the same ability as Ascalon II, it is still quite strong. Issei fused it to the tail of his armor to create the Tail Blade ability to suprise enemies with a third arm.
Mjolnir Replica (Temporarily): During the battle against Loki, Issei was temporarily lent a replica of the legendary war hammer used by the Norse God of Thunder. At first, he was unable to wield it due to harboring evil thoughts, which were his perverted desires, though he became capable of using it after being blessed by Chimune Chipaoti. He later returned the hammer after Loki's defeat.
- (Issei shouting out his dreams): I’m going to become a Harem-King! (Volume 1, Life 2)
- "I’m dumb so I don’t know anything about “foreseen” or “checkmate”. But I can still fight. I can continue fighting as long as I can crunch my fist!" (Volume 2, Life 5)
- "President Rias Gremory's virginity belongs to me!" (Volume 2, Life ∞ vs Power ∞)
- (To Rias):"President! I don’t have talent for swords like Kiba! I’m not a genius like Akeno-san at using demonic-power! I don’t have a crazy strength like Koneko-chan, nor do I have a healing power like Asia! Even still, I will become the “Strongest Pawn”! For you, I will even beat God! With this Boosted Gear! My only weapon! I will make sure that I will protect you!" (Volume 2, Life ∞ vs Power ∞)
- (To Rias): "Then I will give my right arm as a price next time. Then my eyes if another one comes in. I will keep on saving President. That’s the only thing I can do. But I will definitely come and save you. That’s because I am Rias Gremory’s [Pawn]." (Volume 2, Last Kiss)
- (To Yuuto): "Kibaaaaaaaa! Cut down both Freed and Excalibur! You are the “Knight” of the Gremory group and my comrade! My friend! Fight Kibaaaaaaa! Don't waste their feelings and spirit!" (Volume 3, New Knight & New Rival)
- (To Gasper): "...Are you scared? Of the Sacred Gear...and of us? “I also possess a Sacred Gear in which the strongest Dragon resides in. However, my life was not as amazing as yours, who was a Vampire, or like Kiba’s. I was a normal male high school student. I...to be honest, am scared. While using the Dragon’s powers, I feel that some part of my body is changing into something else. I don’t know much about Devils right now either, or about what a Dragon is. However, I feel like I want to proceed further." (Volume 4, Life 3)
- (To Akeno): "Ah, how do I say it, Akeno-san, you’re a kind Senpai. No, um, I definitely hate Fallen Angels, but I think that Akeno-san is different. Even if you have the blood of Fallen Angels in you, Akeno-san is Akeno-san, and you are the Vice President of the Occult Research Club. I have never once had thoughts of dislike towards Akeno-san. Even after hearing that Akeno-san has the blood of Fallen Angels, I cannot come to hate you. I like you even now, so there’s no problem, right? Huh? What the hell am I saying? Sorry, no more sensitive words are coming to me..." (Volume 4, Life 3)
- (To Vali): "I’m going to kill you, you bastard....Just as you said, my father is an ordinary office worker who works from morning to evening for our family. My mother is an ordinary housewife who makes delicious food for our family morning, noon and evening. However, they raised me up to this point. To me, they’re the best parents...Kill them? My father and mother? Why should they have to be mixed up in the situation of someone like you and be killed? As if I know anything about things like valuable or destiny!" (Volume 4, Life 5)
- "Stupidity is fine! If I can't win with ability, I'll excel through stupidity!" (Volume 4, Life 5)
- (To Koneko): "Koneko-chan…though I have a legendary dragon lodged in my body, I can’t do anything…If I had gotten stronger those times with Asia and Buchou, if I had displayed my dragon power, they wouldn't have had such sorrowful experiences…—I’m a talentless and useless devil. Even though all the previous Sekiryuuteis achieved Balance Breaker in a short time…it will take who knows how many months for me. I understood that. I already understood that from the very beginning. Even though I possess the power of the Sekiryuutei, it’s wasted on me. Because I’m useless…I can’t do anything for you, Koneko-chan. I thought I could at least become a shield for you, but…" (Volume 5, Life.3)
- (After attaining Balance Breaker): "Balance Breaker, [Boosted Gear Scale Mail]! It’s been achieved here by poking my master’s breasts!" (Volume 5, Life.3)
- (To Kuroka): "Don’t make my cute kouhai cry. If you aim at Koneko-chan again, I won’t stop my attack next time. You may be a woman and Koneko-chan’s onee-san, but you’re my enemy!" (Volume 5, Life.3)
- (To Koneko): "I’ll declare this to Koneko-chan too. Even if you run out of control with your nekomata power, I’ll stop you. I want to use this Sekiryuutei power not only for myself, but for my friends too. And even if that scary onee-san comes again, I’ll definitely save you. Since I’ll blow away that nee-chan with a punch, you don’t need to be scared." (Volume 5, Life.4)
- (To Genshirou): "Come, Saji. Come! Sajiiiiiiiiiiiii! You won’t let it end here, right!? You don’t intend to let it end like this, right!? Weren’t you going to do the things that aren’t possible for idiots like us and run swiftly forward!?" (Volume 5, Life.5)
- "Hey, Saji. Which one of us will advance to being a high-class devil first and have our dreams granted? I—won’t lose! Absolutely. And next time we fight, I’ll win for sure! So, until next time. My rival, Saji Genshirou." (Volume 5, WINNER)
- (To Diodora): "Don’t make our Asia cry!" (Volume 6, Life 4)
- (To Diodora): "Don’t ever get near Asia again! The next time you show yourself before us, then that time I really will blow you away!" (Volume 6, Life 4)
- (To Asia): "I…..! I……! I made an oath that I won’t let Asia go through sadness again! That’s why I won’t let you do that! I will protect you! Yeah, I will! I will definitely protect Asia!" (Volume 6, Life 4)
- (To Asia): "Asia, stay by my side forever. You aren't allowed to leave me again." (Volume 6, New Life)
- "That's because we have to look if there is an Oppai in front of us!" (Volume 7, Life 2)
- "I….will become the 'Ultimate Pawn', and I will be alright if I can become a high-class devil. I’m aiming to make my own kind of a harem." (Volume 7, Life 3)
- (To Akeno): "……I will just stay like this and hug you! I won’t do ecchi things to you! I….I am lecherous! I really want to have sex with Akeno-san! But I don’t want to make love with you with these kind of feelings!" (Volume 7, Life 3)
- (To Akeno): "-I will stay by your side. I will always stay by your side whenever you feel sad. I will hug you like this anytime. So please. Please cheer up." (Volume 7, Life 3)
- "Buchou, I will become stronger for you and my comrades." (Volume 7, Life 3)
- (To Genshirou): "It seems like my road to becoming a Harem-king is rough, so I have to break every single obstacle on my way. For that, I will have to adapt to the power of the Sekiryuutei and other kinds of power and make them my own. –There are many things I want to make a reality and many things I want to protect. I have to walk right ahead no matter what."
- (To Connla): "Due to the things you do, there are those who are crying sadly. No matter what your reasons are, I must blow you away." (Volume 9, Life 4)
- "Sairaorg-san, Vali...and Cao Cao. I won’t lose, and I definitely will become stronger. Much stronger. I believe that, one day, my dreams will come true... Elsha-san, Belzard-san, though we parted in a most ridiculous manner, please continue watching over me from wherever you are. As the Sekiryuutei, as the Oppai Dragon, I will do what I need to do." (Volume 9, Maven)
- (To Lirenkus): "Lirenkus, men shouldn’t cry. You have to become strong so that you can protect a girl no matter how many times you fall, and keep on standing up." (Volume 10, Life 1)
- (To Asia, Akeno and Koneko): "…….Asia, Akeno-san, Koneko-chan….I’m scared. I’m actually scared of getting along with girls….. Because it makes me think that the same thing will happen again…..! The girls in our group are being kind to me, but if I tried to take another step and try to get along with everyone, it makes me think everyone will reject me and laugh at me…..! I know that everyone isn’t bad inside my head! All of you are good people! But, I still can’t! The more I tried to understand everyone, the more it makes me stop!……I don’t want to taste…..the same thing again….." (Volume 10, Life 2)
- "I’m Hyoudou Issei. The current Sekiryuutei. I’m also the Chichiryuutei, and the Oppai-Dragon. So I will be fighting while carrying the dreams of many people, huh. I need to take this match with a different feeling to that of the time when I had the Riser-match and Sitri-match. For myself, for Buchou, for my comrades, and for the children supporting me….. Let’s go, Ddraig. There are many things we have to accomplish, but the things we need to accomplish are simple." (Volume 10, Life 3)
- (To Coriana Andrealphus, before defeating her): "You take off the bra, then the pants!" (Volume 10, Life 3)
- (To Sairaorg, before their fight): "I have no grudge against you. I have no hatred towards you. This is just a game. But I will be taking revenge for my comrades. I’m not mature enough to forgive you when you have taken down my comrades……..!" (Volume 10, Life.MAX VS Power.MAX: MAN VS MAN)
- (To Sairaorg): "Today I will claim victory by defeating you, who becomes serious! We are fighting for our dreams! What can we achieve by not defeating our opponent who is at his best!?" (Volume 10, Life.MAX VS Power.MAX: MAN VS MAN)
- (To the past Boosted Gear possessors): "Let's go Senpais! I’m a Sekiryuutei! Oppai-Dragon! The man who is in love with Rias Gremory! I am Hyoudou Isseeeeeeeeeeei!" (Volume 10, Life.MAX VS Power.MAX: MAN VS MAN)
- (To Sairaorg): "Rias Gremory is the woman I love. I want the woman I love to win. I want to protect the woman I love. I want to fight for the woman I love. I……..I! I will defeat you in front of the woman I love and the children who follow me! For my dream! For the children’s dream! For Rias Gremory's dream! Today I will surpass you! I looooooooove Rias Gremory!!" (Volume 10,Life, MAXIMUM VS Power MAXIMUM: Crimson and Red)
- (To Sairaorg): "……Haa…….Haa……. I also have a dream! To make…….Buchou the……King of the game……. I will……also become a King one day! I will become stronger than anyone! I……! I will become the “Ultimate Pawn”……..!" (Volume 10,Life, MAXIMUM VS Power MAXIMUM: Crimson and Red)
- (To Rias): "……I……I want to protect Rias…I want to protect Rias for the rest of my life…… I am in love with you! I love you Rias!" (Volume 10,Life, New Life)
- (To Ouryuu and Bova): "I am indeed disappointed, but we have learnt a lot in this game. In my view, phrases like ‘there’s no meaning in losing’ or ‘there’s nothing to be gained in losing’, are not true okay? Listen up, Bova, Nakiri. Self-attribution is what makes the people who are defeated more powerful. Because — in order to erase any regrets, you must obtain victory." (Volume 23, Life.Youth)
- "I'll never forgive anyone who makes our president cry!" (Season 2 New)
- (To Irina) "No way, no way in hell. I’ve invested my entire aptitude in magic for this. Would you have me develop a technique that allows me to see through women’s clothing instead? I made such a choice bearing my thoughts, worries and all. I shall...I shall destroy more women’s clothes and then...and then...and then someday, as I gain the ability to destroy them just by looking, I shall continue my fight!" (Season 2 New, Episode 3)
- (To Irina) "Lechery is my strength! Lechery is my justice!" (Season 2 New, Episode 3)
- (To Matsuda and Motohama in school) "Boobs are heavier than someone's life." (Season 2 New, Episode 4)
- Issei's birthday is on April 16.
- Issei's name means "Sincere/Honest".
- His surname means "Soldier" in reference to him being a Pawn, as pawns are considered to be foot soldiers in chess analogy. So his full name means "Sincere or honest soldier".
- Despite not officially being a member of the Gremory clan yet, he is already considered one by the members (minus Rias) and their servants. After proposing to Rias, she also considers him a member as her future husband and fiance.
- After his visit to the Underworld and meeting the Gremory family, it is noted that Issei acquired gentlemanly behaviour as well as knowledge about the Gremory clan's history and general knowledge about the Underworld, due to the fact that Rias chose Issei as her lover and future husband, thus requiring him to obtain noble etiquette to serve as Rias' husband.
- Issei is engaged to Rias Gremory, Akeno Himejima, Xenovia Quarta, Irina Shidou, Asia Argento, Koneko Toujou, Kuroka and Rossweisse.
- His first kiss was with his childhood friend Irina Shidou, albeit he was asleep.
- In Rating Game fighting-types, Issei is considered a Power-type while also being a good Support-type due to his Boosted Gear Gift ability.
- According to the Nilrem Magicians, Issei's strength is ranked in SS-Class.
- Issei shares the meaning of the series' title that refers to Great Red: "Dragon of Dragons" as he can be considered a mini Great Red, who the title mainly refers to.
- He along with Vali have made another meaning for the title that refers to themselves: "Diabolos (Devil) Dragon".
- Issei's life force is currently unreadable due to his body being made from Great Red's flesh and Ophis' powers. At its lowest which is zero, it represents "dream" or Great Red and at its highest which is infinite, it represents "infinity" or Ophis.
- According to Ophis' spawn; Lilith, Issei smells like her, Ophis, and Great Red.
- According to Elmenhilde, Issei's blood tastes sweet, mellow, and rich, and is absolutely addictive.
- Issei is very popular in Norse mythology as many people in Valhalla were cheering for him.
- Issei is said to be particularly good with children.
- According to Rias, Issei is the type of man that is liked by older women.
- According to Ddraig, Issei is the first host he has fun making conversations with.
- Issei is also the first host to treat him as a single entity rather than a tool.
- Issei's contract requests as a Devil tend to be with eccentric clients, such as Mil-tan and Morisawa.
- His favorite type of cake is cheesecake.
- Issei's key words are guts, effort and peace.
- Issei is the only person outside of the members of the Slash/Dog Team that is allowed to read Vali Lucifer's Black History Diaries.
- Issei has a tokusatsu show in the Underworld called Breast Dragon Emperor Oppai Dragon (乳龍帝お, Chichiryūtei Oppai Doragon), which stars him as the main character named Issei Gremory and it is considerably popular among the children.
- Issei makes review videos for Oppai Dragon products while acting as the "Oppai Dragon" himself and uploads them to DeviTube. This caused the merchandises' sales to increase.
- It would seem his erotic nature is hereditary, as his father, grandfather, mother and grandmother all have a erotic nature too, with his father and grandfather also seeking to create a harem when they were younger and his mother teaching Asia about the naked apron while his grandmother teased Issei and Asia about the two of them having sex together and creating a child.
- According to Kiryuu, Issei is well endowed, as she believes that he can satisfy both Asia and Rias with his size.
- Issei has a secret stash of his porn collection that he kept perfectly hidden within household goods inside the closet located in an unused room, he was surprised to hear that some of the girls not only found it but also have been watching them.
- Issei has broken off all the engagements of the female characters placed into one, (Rias, Kiyome, and Rossweisse) all of which have fallen in love with him as a result.
- Issei is shown to be a talented sculptor as he was able to create a perfect clay replica of Rias.
- Issei is good at sewing, as he was able to sew together headbands for the entire Occult Research Club in preparation for the dodgeball tournament.
- Issei has a strange reaction to alcohol, as he becomes more serious and shy when drunk.
- Issei is very good at giving massages, so much so that it's too erotic for women.
- Issei is the only man in existence to have seen Gabriel in a bikini, as well as the most beautiful women in all of Heaven who serves under her; in an old school swimsuit, transparent negligee, and athletic clothing.
- Issei's first-ever meeting with Asia may have been foreshadowing to the relationship between Cleria Belial and Masaomi Yaegaki, as at first, Issei and Asia similarly to Cleria and Masaomi, were forbidden from seeing each other in the same town; Kuoh Town due to the Devil's side and Angel's side still at feuds with each other.
- Issei is being supported by the New Satan Lucifer faction due to the fact that he is Sirzechs Lucifer's future brother-in-law, as they hope to boost his political influence and bring him into their faction.
- After the defeat of the Alliance of Hell, Issei is considered as a potential candidate for the new Satans.
- Sirzechs wants to create a new seat for Issei under the title Satan, as in the Revelation of Apocalypse, it is recorded that the terms of Satan and dragon were synonymous, which suits Issei as he possesses the flesh of Great Red who appears in the Apocalypse. Sirzechs also wants to bestow his title of Crimson Satan to Issei.
- Issei is one of the protagonists of the erotic doujinshi called "Prince x Beast" alongside Yuuto Kiba, that the Kuoh Academy Manga Club produces, as it is based on the misunderstanding that the female students have about Issei's and Yuuto's relationship, with the manga being popular among the female students of the academy.
- Issei is a fan of Dragon Ball (Drag-so Ball in the Anime and Manga) and Gundam.
- He sometimes likes to create Gundam plastic models when he has personal free time.
- Issei has loved robots and space battleships since he was a child.
- Issei is shown to have liked fishing when he was younger but gave up on it after he destroyed his father's favorite fishing rod. However, he regained his passion for fishing later on.
- Issei's appearance is based on Kazuma Torisuna from s-CRY-ed because the author is a fan of the series.
- In the Light Novel, Issei's Dragon arm is depicted as a scaly Dragon arm that covers his entire left arm, while in the anime, his Dragon arm is replaced by the Boosted Gear.
- The manga depicts Issei's Dragon arm as a combination of both.
- Supposedly, one of Issei's power-ups was to involve sucking Rias' breasts. Unfortunately, that was already too much for Fujimi Shobo, so the author resorted to something else.
- In the anime, Issei shows symptoms of PTSD and trust issues thanks to Raynare.
- In the short story "25 (Twenty Five) at the Clubroom with Rias-buchou!", Issei was stated to have black hair; however, the anime and light novel illustrations portray him as having brown hair.
- Issei was originally envisioned with Kiba's character traits but later changed into a pervert because Ishibumi felt those character types were too "weak" for the main character.
- Issei was originally going to be just a human who helps Asia.
- In the English dub, Issei’s nickname Oppai Dragon is Grabbin Dragon.
- His seiyū, Yūki Kaji, eventually married Ayana Taketatsu, the seiyū of Koneko, on June 22, 2019.
- Ishibumi's twitter
- Light Novel Volume 24, Life.0
- Light Novel Volume 5, Life.2 The gathering of the Young Devils!
- Light Novel Volume 8, Extra Life. The Fun Gremory Family.
- Light Novel Volume 22, Life.3 Gremory’s Graduation Ceremony
- Light Novel Volume 22, New Life
- Light Novel Volume 23, Life.Youth Because of this Youth
- Light Novel Volume 23, New Life
- Light Novel Volume 24, Life.5 The Death God and the Hyoudou Family’s Breast Technique
- Light Novel Volume 25, Life.DxD VS Life.GOD Challenge to the Gods —Red Dragon—
- Light Novel Volume 18, Christmas
- Light Novel Volume 14, Life.3 Maverick Magicians
- Light Novel Volume 14, Life.2 The Rulers of the Late Night
- Light Novel Volume 16, Life.2 The Kins of the Dark Night
- Light Novel Volume 25, Life.3 The Battle at Yggdrasil
- Light Novel Volume 9, Life 3
- True Light Novel Volume 3, Life 2
- Light Novel Volume 6, Life 2
- Light Novel Volume 13, Extra Life
- Light Novel DX.5, Life 3
- Ishibumi's Twitter
- Light Novel Volume 24, Life.2 The God of Death and the Dog of the Blade
- Gremory of the DeviTube
- Light Novel Volume 3, Life.3 The Plan to Destroy the Holy-sword!
- Light Novel Volume 11, Life.1 Study and Mating Season?
- Light Novel Volume 18, Life.1 Even Devils Celebrate Christmas!
- Light Novel Volume 4, Life.2 Class visit Begins
- Light Novel Volume 3, Life.1 Life.1 Heat Up Occult Research Club!
- School Heroine
- Fantasia Heroine Calendar Book 2014
- Light Novel Volume 23, Upsetting sorcerer.2
- Light Novel Volume 15, Episode Issei 2
- Light Novel Volume 18, Life.2 The Forbidden
- True Light Novel Volume 4, Bael
- True Light Novel Volume 4, Life 0
- Light Novel Volume 24, Secret talks
- Light Novel DX.2, Life.2 Student Council's Decision
- Light Novel DX.2, Life 6
- Light Novel Volume 24, Life 5
- Light Novel Volume 25, Life 0
- Light Novel Volume 20, Parents
- Light Novel Volume 23, Life.2 Dragon Attracts Dragon
- Light Novel Volume 5, Afterword