Mahiru Hīragi/Relationships

Kureto Hīragi
Mahiru's half-brother, a fellow member of the prestigious Hīragi family and the most likely to become the next leader of the JIDA. He says he trusts Guren and sends Guren on an extremely dangerous mission to Nagoya. He wants Guren to work for him and his ambitions, but Mahiru wants him to follow her. Mahiru often played with Kureto when her demonic side got stronger. She later fights Kureto when she was a vampire and overpowered him not before leaving even though she stated that she would kill him.

Seishiro Hīragi
Mahiru's half-brother and a higher-ranking member of the JIDA. A member of the prestigious Hīragi family. Mahiru, being Seishiro's superior in combat, is completely unafraid of and able to intimidate him. Despite Seishiro resenting her, in return Mahiru shows nothing but utter disgust at Seishiro for his behavior to the point of even saving Sayuri, who Mahiru dislikes for loving Guren, from him.

Shinoa Hīragi
Out of everyone in the Hīragi family, she was the only one who Mahiru genuinely loved and cared for. Although, according to Shinoa, they were not close; she explains that the Hīragi children are raised without knowing familial love, but Shinoa appears to care a lot about her eight years later. In truth, Mahiru worried for Shinoa deeply when she was still human. After realizing the Demons residing within their bodies due to their heritage were slowly consuming their minds with age, Mahiru in desperation managed to remove the Demon in Shinoa and bore two demons in her own body to protect her from becoming a Namanari. Days before the Apocalypse, Mahiru had Guren pass Shikama Doji to Shinoa, returning her the demon she was originally born with so that Shinoa will survive the Apocalypse.

Shinya Hīragi
When they met for the first time as ten-year-olds, Mahiru told him she would never fall in love with him as she already had someone (Guren). Had Mahiru openly stated to her family she did not want Shinya, they would have disposed of him; on the other hand, Guren was not allowed by her family. For these reasons, they both agreed Shinya would be her cover-up fiancé until she could be with the person she loved.

Later on, when Guren and his squad found Mahiru performing a ritual in Seraph of The End nearly prior to the apocalypse, Shinya made the mistake of angering her for her obsession with Guren and in a rage, she remorselessly and violently killed Shinya in anger.

Tenri Hīragi
Mahiru's father Tenri held favoritism towards her for her power and intelligence, and had planned to make Mahiru become the next leader of the Hīragi Family. Mahiru also stated that she is "sure" that Tenri places "much more" trust in her than Kureto, because she was stronger. The disgrace she earned by becoming a demon was extreme enough to ignore the existence of her half-sister, Shinoa Hīragi.

Akane Hyakuya
In the light novel, she speaks to her to find out she has a crush on Mikaela.

Junji Hyakuya
When she arrived to adopt him as Miyuki Yamada, Junji was initially nervous and adamant about not going with her and staying at the orphanage. After being calmed down by Mika, Mahiru reassured him that he'll like it with her and he willingly leaves. Shortly afterward, Mahiru murders someone in front of him and knocks him out, and when vampires attack them, she protects Junji.

Mikaela Hyakuya
As Miyuki Yamada (Mahiru Hiragi) she talks with Akane Hyakuya and realizes she has a crush on Mikaela.

Saitō
The former second progenitor of the vampires, he and Mahiru worked together for the Hyakuya Sect. They appeared to have cooperated well with each other.

Yuichiro Hyakuya
When he was in locked up in a cell, she spoke to him briefly about being a demon spawn. She asks him why he thinks like that, adding that he looked human to her and demon or not, he should get to live. Before leaving, she told Yu to stay strong and that one day she'd come back to free him from the Hyakuya Sect, prior to the researchers messing with his memories.

Norito Goshi
A member of Guren's squad since he was 15 back in high school prior to the apocalypse. He enjoys making fun of Guren. A member of the prestigious Goshi family.

Sayuri Hanayori
For her crush on Guren, Sayuri is jealous and dislikes Mahiru as she can never win Guren's heart. Mahiru equally dislikes her as well, sadistically taunting her on how she can never be with Guren and outright revealing that she did it with Guren out of spite. Although at one point, she saved her from Seishiro, she appeared to dislike having to do so and even expressed her jealousy of Guren's care for Sayuri by angrily telling him that he is too weak and cares for her, further infuriated when Guren mockingly says that she did well. As a vampire, Mahiru's dislike of her has apparently intensified, being clearly displeased when Guren touched Sayuri's breast to save her in front of her and later on killing her.

Guren Ichinose
Mahiru's lover. According to Shinoa, all Mahiru wanted was to love him, but the family did not approve. Mahiru's desire to be with Guren was what caused her to turn against the Hiragis. Even when in her Namanari form, she still loves Guren and would not kill him, but is not above being cruel and fully willing to non-lethally harm him, and she is motivated to make sure Guren gave in to his Demon and be with her. She is shown to be particularly cruel towards any girl with a crush for Guren, displaying a strong possessive side. Even before being taken over, Mahiru already showed this rage towards Sayuri and Shigure, quickly turning dark when Guren nonchalantly praised them in her back. Along with that, she was also deeply distraught by Guren's coldness towards her. Her human personality was able to resurface at times and she showed deep remorse for what she had put Guren through and tried to ensure his safety whenever her demon put him in potential danger. On his part, Guren's love remained as strong as ever and he desperately tried everything to save her, even trusting her human side and even making love to her, which she would later on flaunt to Shinoa, even going as far as to actually describe how she felt when they did it. Prior to the apocalypse she lied to Guren multiple times to protect him from the experiments she was doing and other dangerous places to keep him safe but she eventually had a final confrontation with Guren and his squad where she effortlessly kills Guren's teammates but leaves Guren alive and bitterly asks if Guren hates her now, but Guren never hated her or resented her and only wanted to save her, which moved Mahiru to tears as she stabbed herself using Noya (which had a seal on it already). With her demon and human side merged, Mahiru retained her love for Guren as Mahiru-no-yo and she is delighted whenever Guren chats with her in his mind. Although not above taking control at times, she mostly allowed Guren to do whatever he does. She manifests quite often when Guren mentions her or Shinoa, much to her happiness which she sometimes complements him, though he ignores her. Indeed, Mahiru went as far as to comfort Guren in her demonic form, willingly shouldering the blame of causing the Catastrophe along with him.

Mito Jujo
Mito utterly adored Mahiru in high school, as she admired her for her strength and kindness, and even called her a "goddess". On Mahiru's part, just like with Sayuri, she dislikes her for her love for Guren, sadistically showing pleasure at the idea of her painfully dying. As a vampire, she is even more resentful, coldly rebuffing Guren for caring for her in front of her and killing her.

Shigure Yukimi
A member of Guren's squad since she was 15 back in high school prior to the apocalypse. She does not speak often. Mahiru resents Shigure just as much as she resents Mito and Sayuri due to her love for Guren. Hearing Guren praise her visibly infuriated her. She flaunted the fact she had did it with Guren gleefully to Shigure and as a vampire coldly rebuked Guren for caring for her in front of her and killed her.

Krul Tepes
She was the one who turned Mahiru into a vampire, and they made a deal with each other eight years before the apocalypse. When meeting with Guren, Krul asked if he was a messenger of Mahiru, and immediately declined when she thought he wasn't. When burning in her ten days of exposed torture, Krul acknowledges that Mahiru kept her side of the bargain after finding out that her brother is inside Yu's sword.

Ferid Bathory
She and Guren come across him at a zoo. He was able to see her while she was a demon hinting at the possibility of them working together.

Asuramaru
Mahiru formed a contract with him while she was human. Nothing is ever explicitly shown about how their relationship was, but it can be assumed that it was solid, judging how he was obedient to her when she called his name.

Shikama Dōji
The demon currently contracted with Shinoa. Mahiru formed a contract with her when she was human. It is later revealed that Shikama Doji may have possessed Mahiru prior handing it to Shinoa who was capable of resisting Shikama Doji thanks to Mahiru protection.

Byakkomaru
Mahiru meets Byakkomaru when Guren Squad leaves to go Osaka. Byakkomaru is immediately able to tell she is not a demon but decides to not do anything about it unless she hurts Shinya. Mahiru likely thinks lowly of Byakkomaru because she calls him a beast.

Noya
Mahiru is the one prepared him as a demon weapon for Guren, she eventually used him to stab herself and then she integrated him with it in her heart; spreading the curse all over Mahiru and Noya absorbed her in the process thus transforming it into Guren current demon, Mahiru-no-yo.