The Red Dragon Emperor's Awakening[]
Sirzechs made his first appearance in Volume 2 during Rias' engagement party, where he indirectly (but purposely) helped break off her engagement with Riser Phenex.
Birth of the Breast Dragon Emperor[]
In Volume 4, Sirzechs went to the Kuoh Academy along with his father for Rias' class observation day. Later, he and Serafall Leviathan were sent as the representatives of the Devils during the peace conference between the Three Factions, which was invaded by the Khaos Brigade. Despite so, the peace talk ended without any serious problems, and the leaders of the Three Factions successfully signed a peace treaty.
In Volume 5, he and the rest of the Satans attended the opening ceremony for the Young Devils Gathering, asking each of them to speak out their dreams for the future and starts the Rating Game for the Young Devils Gathering by arranging a Rating Game between his sister, Rias, and Sona Sitri, Serafall's sister, handing a medal to Saji after the match for his excellent performance.
In Volume 6, Sirzechs appears in Rias and Diodora Astaroth's Rating Game, which had been interfered by Khaos Brigade's Old Satan Faction where he confronted one of the leaders of the Old Satan Faction, Creuserey Asmodeus, attempting to reason with him to no effect before being forced to fight and kill him.
The Heroic Oppai Dragon[]
Sirzechs as "Satan Red" fighting Issei
In Volume 8, Sirzechs appears in the Hyoudou residence during his supposed meeting with the other Satans, informing Rias that she will be undergoing a ceremony at the Ruins of Connection. Later on, he, Grayfia, and the other Satans acted as the Satan Rangers during the trials at the Ruins of Connection where he fought against Issei in the last trial and was able to overwhelm Issei with ease even after Issei used Rias' breasts as a power up.
In Volume 9, he and Azazel has a conversation on the Hero Faction, talking about how they are gathering Longinus and Balance Breaker users in their organization.
In Volume 10, he appears after Issei's battle with Sairaorg informing him about his promotion test to Middle-Class Devils.
In Volume 11, he revisits the Hyoudou Residence to get the confirmation of Issei, Akeno, and Yuuto for the middle-class promotion, telling Issei he can call Rias by her name even in front of him before once again telling him to call him brother, which caused him to be hit by Grayfia using a harisen, telling him that he is going overboard. He also arranges for Ravel to become Issei's manager.
In Volume 12, during the Demonic Beast Riot, Sirzechs and Azazel went to the Realm of the Dead to confront Hades, the God of the Realm of the Dead, attempting to prevent Hades from making any moves on the Underworld. Sirzechs later reveals his "true form" to comply with Hades' demand but warns him that he is unhappy with what Hades did to his sister, Rias, and his brother-in-law, Issei, and assured him that should they fight, he would eliminate him without restraint or hesitation. Afterward, he and Azazel discussed about the aftermath of the crisis as well as about "one", known as the individual, and the "circle", known as the group.
The Legend of Oppai Dragon and his Lively Companions[]
Sirzechs was seen at the end of Volume 17, talking with the captured Euclid, asking why Euclid did such actions and comments that Issei is a brother that he can be proud of which Euclid sarcastically apologizes that he couldn't do the same while calling Sirzechs naive.
Sirzechs was seen talking to Azazel in the latter part of Volume 18 where they talked about the floating island Agreas that was stolen from them by Rizevim. Sirzechs told him that what was inside the island was essential for the creation of the Evil Pieces and the Brave Saint cards. He also told that there are only one thousand sets remaining and it is crucial for them to retrieve the island as the Evil Pieces has already made a deep impression on the culture of the Devils and the Underworld.
Sirzechs with Elmenhilde and Azazel
In Volume 21, during the Evil Dragon War, Sirzechs appears to help Issei when fighting against the 666's core. After both of them fail to deal any sufficient damage on 666, Sirzechs assembles his peerage to implement Azazel's plan of trapping 666 inside the Isolation Barrier Field. Before leaving, Sirzechs hypnotizes his wife Grayfia, leaving her behind much to her dismay as Sirzechs proceeds to depart along with the remaining members of his peerage while Issei looks on in distraught.
Red Dragon Emperor of the Blazing Truth × White Dragon Emperor of the Morning Star: The True Dragon(s) of the Kuoh Academy[]
Sometime after Issei's match with Baraqiel in Volume 22, Ajuka had summoned him to his personal research facility in the Satan’s territory, there he showed him a large screen displaying a live broadcast of Azazel and the others in the Barrier Field who were battling Trihexa. They reveal that communication is possible and also that supplies are regularly sent over for them and that it's currently confidential with only a few people are aware of it. Sirzechs was the third to appear on the monitor, he was relieved that Issei was alright after they parted last time. He, Azazel and Ajuka revealed the reason for this meeting was that they're establishing a secret intelligence bureau called EXE and they want Issei to be its intelligence officer, with the establishment being planned for 2 to 3 years from now after dealing with the post-war rehabilitation and the management of the international tournament. While he is not confident enough about taking such a role, Sirzechs told him that for now he will need to learn together with his team over time, he responds by saying he will think about it.
In Volume 23, Issei paid a visit to Ajuka's research facility to speak with the former leaders once again. As he explained the events that has happened since then, Sirzech congratulated him and was also happy that his younger sister was also on a winning streak, he exclaimed that he could fight Trihexa now with a peace of mind while landing a stunning blow on the beast.
In Volume 24, Sirzechs and Azazel talked with Ajuka about the successions of the new 7 Great Satans System with their agenda being to have Issei and Vali to be named as 2 of successors, although they heard politicians associated with the first-generation Bael raised objections to this. When Sirzechs question the minimal condition for them to succeed, Ajuka confirmed those must at least be within the top 4 of the tournament They also worried over Hades taking action behind the scenes, but Azazel showed confidence that the Two Heavenly Dragons will handle it.
When discussing which title would suit Issei best, Azazel leaned more towards Asmodeus as it represents lust, though Sirzechs recommended a special 8th seat just for him, a comment that stunned Ajuka while Azazel laughed. Sirzechs desired to pass on his Crimson Satan title to his "brother-in-law", Ajuka promised to pass on his words to Issei and Rias. He then expressed looking forward to seeing his nephews and nieces in the future, Azazel jokingly added that there will be a ton of kids with different mothers, he even assumed that Sona may have children then. Serafall objected his statement saying any of Sona's groom candidates must be stronger than her and defeat Sirzechs, whom the latter was brought in one-sidedly but had no objections. Odin and Zeus then joined in on the conversation which was soon changed to about their kids who will be going up against Issei soon.
In True Volume 4, Sirzechs overhears the talk between Ajuka and Azazel, stating that if it's Issei, then surely he would surely become Oppai Dragon again.