Red Dragon Emperor of the Blazing Truth × White Dragon Emperor of the Morning Star: The True Dragon(s) of the Kuoh Academy[]
Ingvild at the fountain and noticed Issei
Ingvild made her first appearance in True Volume 1, and was singing by the fountain where Issei was killed by Raynare. While biking to his house, Issei hears her singing and follows where it is coming from and as she stops singing, she realizes he’s the Red Dragon. They soon get attacked by the unidentified devils and, as a result, Ingvild stands behind Issei. After Issei defeats the unidentified devils, Ingvild is covered in blood from her dress to her face and uses the handkerchief that Issei gave her to wipe the blood from her face. She looked at her hands covered in blood and called it beautiful because it’s more of a crimson color, and Issei’s armor is the same color as well. Ingvild then vanished without a trace after Issei called in Rias. She appears again after Issei and his friends are fighting the unidentified devils, and she starts singing again, which causes Issei and Bova Tannin to partially kneel down in pain while affecting Ddraig as well. To stop her singing, Rossweisse wrapped her in a light blue aura, and used her hypnosis magic to control Ingvild as well as make her temporarily fall asleep.
Ingvild is sleeping in one of the rooms of the Hyoudou Residence and when she wakes up, Ravel sends Issei and Asia to talk to her. Ingvild then asks them to tell her if she is in Issei’s house which Issei confirms and introduces himself and Asia. Ingvild then introduces herself but remembers her surname which the people in the hospital call her: Leviathan. Issei asked her why she was at the fountain, which she answered the sea and also said that she heard that everyone including her parents had already passed away. After having a brief conversation about how Ingvild wants to see the ocean, Asia suggests that everyone go to the beach. While at the beach, Ingvild is standing on the sand and looking at the ocean when Issei goes to talk to her. Issei tells her that he likes her singing and she thanks him for bringing her to the sea, and they converse where she reveals that she was born in the seaside city and loves the ocean. Issei tells her to go to the sea with him, but she says she will be taken somewhere where her powers are going to be studied. Issei, however, tells her he will take her. Ingvild laughs at the fact that she became friends with the Oppai Dragon and Issei tells her to call him by his name since they are friends and invites her to eat with Rias and everyone else, but their conversation is interrupted by Nyx who appears from the sky with the intention of obtaining Ingvild in order to use her to control powerful dragons like Issei, Vali, Crom, Ophis, and Great Red. Nyx tells Ingvild her to sing which causes Issei to suffer pain again, and she passes out due to the brainwashing technique caused by Nyx.
After being brought back to the Hyoudou Residence and being allowed to sleep for a while, Ingvild awoke and overheard Cao Cao's assessment that she would have to be sealed which could result in her being unable to awake again or be killed to prevent her power being misused. Realizing that her power could bring trouble to a lot of people, Ingvild stated that she was okay with being killed. This saddened Issei, who implored her to reconsider her choice as he stated that he would be sad if she were to die, which shocked her. After hearing Asia's plea, Ingvild reconsidered her choice and begged Issei to help her, as she did not wish to lose another friend, to which Issei responded by promising to defeat Nyx. She later was present when Issei and the rest of the Occult Research Club departed to defeat Nyx.
Ingvild was contacted by Issei through Akeno’s breast and asked her to sing for him. She became hesitant at first due to the pain she caused when she sang but agreed when Issei begged once again. Her song has been heard throughout the battlefield through by the breasts of the girls and powered up everyone. After Nyx was defeated, the brainwashing spell that was placed on Ingvild was removed by Rossweisse and she thanked everyone for they did for her. Issei’s queen piece began to glow and Ingvild also glowed, causing Issei to believe that he has found a suitable servant and asked if she can sing while being his servant which he agreed. Ingvild became Issei’s first servant and grew out eight wings due to her being the descendant of Leviathan, to which Issei agreed to help her put her wings away. After becoming Issei’s servant, Ingvild appeared at the Occult Research Club where Beelzebub informed the group that the Olympian gods Hypnos and Oneiros had offered to help treat Ingvild of her sleeping disease to which she agreed.
In True Volume 2, Ingvild appeared in Issei’s dream of him marrying his brides, with Ingvild among the first group and she became confused if she became a bride. In the morning, Ingvild went together with Issei, Ravel, Ouryuu, and Bova to do their morning marathon and she became used to running like she used to run back in her hometown but became harder for her because of her sleeping disease. After finishing the morning training, Ingvild was informed by Issei about her devil job and she was accompanied by him, due to her demonic power being too vast for the teleportation magic circle. Ingvild meets her first customer Lavinia Reni, who thanks her for coming to help her with unpacking for the person who is moving into Kuoh Town, which turns out to be Vali Lucifer. She meets a another member of Slash/Dog Team; Natsume Minagawa, who shook hands with and hopes to get along with her. After finishing her devil job, Ingvild received a white dragon plushie as gratitude from Vali and returned to the Hyoudou office with Issei.
In the night, Ingvild and the other girls catches Akeno and Koneko attempts to seduce Issei in Akeno’s erotic room and she wonders about hugging Issei naked but found it embarrassing, and she and the others ended up sleeping with Issei. Ingvild joined Issei and his team to their training camp in the mountain for training, she began her training at the small river to master her water magic in a form of an eastern dragon, and trying to master her clan’s specialty Sea Serpent of The End and after putting back the water back into the river, Ingvild started to feel drowsy and took a break from her training. Ingvild and the two teams celebrated Issei and his team victory at the Hyoudou Residence and as Issei recalls the second-year students' trip, he tells Ingvild to fun at Kyoto, which she happily agrees.
In True Volume 3, Ingvild was half-asleep during the meeting of the Occult Research Club about doing a program they will be doing during the autumn event at Kuoh Academy. The group began talking about Kyoto, with Issei telling Ingvild to enjoy Kyoto and doesn’t need to worry when she is with Ravel and Koneko, which she happily agrees and tells Ravel and Koneko that she is under their care. After arriving to Kyoto by train, Ingvild and the second year students were at the Kyoto Sirzechs Hotel to meet up with Issei and Rias at the cafe to discuss the recent attack from Gressil and Sonneillon, but she was sleeping in the middle of the meeting until Issei woke her up to inform her about the battle coming and told her to wait in the hotel, but she insisted that she wants to participate because she believes it’s fate as she is one of his peerage.
Ingvild and her fellow second year students and teachers gathered in the uninhabited forest of Iwashimizu Shrine to wait for their enemies to appear and was sleeping during the conversation and as the artificial devils appears, she eventually woke up to summon a water dragon and asked for Ravel for instructions, who is shocked at the sight of the water dragon. She unintentionally launched her water dragon at the artificial devils and became worried that she wasn’t supposed to attack them yet, while summoning another water dragon and later she protected Ouryuu from a artificial devil.
In True Volume 4, Ingvild and her friends watched the match between Team White Dragon Emperor of the Morning Star and Team Journey to the West, which ended up on Vali’s victory. Later Ingvild and the group relaxed at the hotel lounge after watching the match and after that she joined Issei and Ravel to meet with Le Fay so she can observe about the Devil and Magician contract until they were attacked by Meredith Ordinton and the fake version of Ddraig, but they managed to drive them away after the others arrived to assist them.
At the VIP room of the Hyoudou Residence, Ingvild watched the group discussion about the change of Issei’s personality and quietly remembered about Meredith’s words to Issei about liking his current self. When Ingvild and the group arrived to England and talked about a plan to fight against the Alliance of Hell, Ingvild was told by Ravel to stay by her side to support and to use her song once Issei returned to normal, becoming a member of the support team of Issei and Vali.
In the final battle against Hades, Ingvild and the members of Team DxD and their allies arrived to assist Issei and Vali, where she used her Sacred Gear to increase the powers of Issei and Vali. After the battle, Ingvild celebrated their victory at the garden of the Hyoudou Residence.