Toujou Household
Basara Toujou[]
Her childhood friend and next-door neighbor during their time spent in the Hero Clan. Both Yuki and Basara were close to where the two would often spend the nights at one another's house. It was noted that she had feelings for him when they're kids, often sleeping next to him and Kurumi during stormy nights, due to her fear of thunderstorms. During the incident where Saito lost control over himself after being possessed by the evil spirit within Brynhildr, unlike a lot of the villagers, including Takashi (and later Kurumi), Yuki didn't hold a grudge toward him for erasing the dead children's bodies with Banishing Shift alongside Seito and erasing the evil spirit too, having been saved by him and remained after he was exiled by the Elders.
Despite being apart from each for six years, Yuki maintained her feelings for Basara and even trained herself for his benefit alone, resulting in her contract with Sakuya. As shown in Volume I, as long as it was for his safety, she would even kill Mio, even if it ended up with him hating her for it. In Volume II, to protect Basara, Yuki even fought against Takashi, despite knowing that she would be killed by him or punished for going against their mission. In Volume III, after she found out about the Master-Servant Pact between Basara and Mio, she decided to form one with him as well and displayed greater loyalty toward him than Mio, his first servant.
In Volume IX, after being used by sacrificial pawns by the Elders, Yuki and Kurumi decided to leave the Hero Clan and abandon their surnames to live with Basara at the cost of also losing their weapons, then furthered their bond alongside Kurumi prior to his fight with Celis.
Kurumi Nonaka[]
As sisters, both Yuki and Kurumi have been shown to be rather close to one another from the time the two were children. Although not much is shown about their relationship in Volume II, due to their conflicting feelings toward Basara for what happened six years ago, she later trusts her little sister to watch over an unconscious Basara as soon as she settled her personal feelings toward him. In Volume IV, as sisters, the two of them are also prone to arguing with one another as Kurumi stated that she was more mature than her older sister after undergoing a far earlier growth than Yuki did, which later caused her and Basara to relieve her after Maria used a Baptism on her.
As her older sister, Yuki has shown to be protective over Kurumi more so than the latter, as in Volume VII, as the usually quiet older Nonako fell into a quiet rage after realizing that Admirath deceived her little sister using Basara and Volga continued talking bad about her, resulting in his swift death. Despite them also being rivals for Basara, both Yuki and Kurumi have shown to be capable of working together in submitting to him and pleasuring him as a team, with neither being ashamed about what they do.
Mio Naruse[]
Although, Yuki and Mio started off with a normal relationship with the latter not knowing that the former was from the Hero Clan. The two began as hostile toward each other when it came to Basara, with Yuki not hesitating to at one point kill Mio if she ever endangered Basara as shown in Volume I not as a Hero, but as someone who cares about him. Her initial opinion of Mio started changing after realizing that she cared about him as much as she did having been protected by him by one of the demons under Lars' control to the point of fighting the more powerful demon to protect Mio.
Their relationship soon shifted from hostile to being rivals from Volume I and onward, which is noted during their constant competition with one another.
Maria Naruse[]
Yuki and Maria have shown little close interaction with each other, but the latter has shown to act lewdly towards the former as she did with everyone else living in the Toujou Household. However, the succubus is more careful toward her than anyone else, especially whenever she tries anything when Yuki is asleep, fearing that she might draw out Sakuya.
Celis Reinhartd[]
Similar to Basara, Yuki and Celis are close childhood friends often spending time with one another whenever the latter comes overseas to the Japanese Hero Clan. The two of them are close enough to the point of sharing embarrassing secrets with each other.
Shiba Kyouichi[]
Like many other members of the Hero clan, Yuki is wary to Shina for his monstrous power and incident he makes in past but rarely shown that on the surface. After their battle with Basara group in Volume II when Basara doesn't want Yuki to let go, she stops him out of fear that from his clash with Shiba, knowing that Shiba could kill him. However, after being with Basara and strengthened her bonds with him and others, she lost fear from him. After Yuki and the rest of the Basara family, except Zest and Maria, return to Hero Village and during negotiations Elders where Shiba attempts to strike Basara, she stops him and treats him with her sword without any hesitation or carrying about elders. In Volume XI during the final battle with Shiba during his revenge on Hero Clan, she fights with him despite that he was nearly omnipotent and defeated Basara before.
Hero Clan
Takashi Hayase[]
Takashi is one of Yuki's childhood friends, the two have shown to be close in the past, while there were some times where the two of them (joined with Basara against Takashi) would fight. Though after the incident where Basara killed Seito alongside getting rid of the corpses of his friends and parents (alongside Takashi's mother) caused a strain in their relationship, they still fought together. After Yuki tried to protect Mio from him, Takashi didn't at all hesitate to kill her, but after the battle ended, he defended her from punishment and pushed all the blame onto himself.
Kaoru Nonaka[]
Kaoru is Yuki's mother, they have shown to have a really close relationship and didn't blame her for befriending demons. In order to protect her mother and father from being punished by the Elders, she and Kurumi chose to renounce their names, and they leave the clan to join the Toujou Household.
Shuuya Nonaka[]
Shuuya is Yuki's father, they have shown to have a really close relationship and didn't blame her for befriending demons. In order to protect her mother and father from being punished by the Elders, she and Kurumi chose to renounce their names, and they leave the clan to join the Toujou Household.
The Elders[]
The higher-ups of the Japanese Hero Clan, as Yuki, diligently follow the order given to her, even if it meant that Basara will hate her if she ended up killing Mio. Eventually, soon after Yuki and Kurumi returned to the Hero Clan in Volume XI with Basara and Mio, she lost all trust in the Elders after they decided to let Shiba kill both sisters if Basara lost against Celis to maintain their political power.