Toujou Household
Basara Toujou[]
Much like Yuki, Takashi, and Celis, Basara was an important childhood friend of hers to the point of even treating him like an older brother; often referring to him as Basara-niichan. However, their relationship soon became far more strained after the incident five years prior to the series after Basara erased Seito who had been possessed by the Evil Spirit sealed in Brynhildr, as well as the bodies of the children and adults who had been killed beforehand. This strain appeared to be more due to the emotional impact that it had on her older sister than with his and Jin's exile, which spurred Yuki to become stronger and Kurumi to become stronger to protect her older sister.
During their reunion in Volume II, she has shown nothing much but hostility toward Basara, even calling him a traitor for protecting the daughter of the former Demon Lord despite being a former hero. Kurumi showed no hesitation to attack Basara, especially after seeing him seemingly attacking Yuki in an attempt to separate the two of them. Her anger toward Basara began to diminish after he rescued her from falling after her link with the spirits was cut off for a moment, and it vanished completely after seeing that he had been suffering more than either of them from the incident from five years ago, even going back to calling him Basara-niichan as she did before.
From Volume IV and onward, Kurumi started to acknowledge her romantic feelings toward Basara, even desiring to form a Master-Servant Pact with him, but couldn't due to the chances that the Elders might find out about it. It was then that Kurumi just started to use her Spirit to form a relationship with Basara in her dreams. Despite not forming a Master-Servant Pact with Basara, she had engaged in several limited sexual encounters with one another sometimes with the other girls; even being the second girl after Zest to give him oral in Volume VI.
Yuki Nonaka[]
As sisters, Kurumi and Yuki have been shown to be rather close to one another from their childhood, spending a lot of their time together with Basara, Takashi and Celis. After the incident involving a possessed Seito and Basara losing control of Banishing Shift, Kurumi started to become more protective of Yuki and growing stronger to do so. But, as sisters, there are times when the two of them argue with one another, such as when it comes to competing with one another for Basara or who is more feminine. In Volume IV, after witnessing Mio and Yuki serving Basara, she questions their lifestyle before Maria teases her about trying to be more mature than her sister, which soon leads to Kurumi being affected by an aphrodisiac. Basara tries to relieve her via massaging her boobs before Yuki licks her armpits, with this being the discovery of her weak spot. When the sisters align with Mio’s travel to the demon realm, they express concern for each other at several points such as when Kurumi loses to Admirath. Yuki and Maria then save her from Admirath when he tries to attack her while she is recuperating. Returning to the human world, they both become victims of Maria’s morning pranks. The Nonoka sisters then become the important characters of Vol IX, tagging along with Basara, Mio, Maria, and Zest to meet the elders. She meets her parents again before Shiba Kyoichi appears and threatens them all. To help Basara prepare for his duel with Celis, Kurumi and her sister have a pseudo-threesome with him, during which they both perform oral on him and Kurumi fingers Yuki’s butt. Kurumi ultimately gets to tie the vow with Basara before Yuki, which she apologizes for. She loses her virginity to Basara and Yuki gets revenge on her for fingering her in Vol IX and ties the vow. Kurumi participates in the final battle against Shiba, and after their victory, she fully moves into the Toujou house. They share their hyper sexual lifestyle of the harem and spies on Yuki when she and Basara have sex in the yearbook club room. They both become pregnant with Basara’s child and marry him.
Mio Naruse[]
Kurumi and Mio started off as enemies at first in Volume II, as the former was charged with killing Mio as an S-Rank Elimination Target instead of being an Observation Target. After moving into the Toujou Household, their relationship remained unfriendly, Kurumi often refers to Mio as "You" instead of by her name. Though, they soon started growing close to one another to the point of taking baths with one another and as a group. Kurumi often also has the same reactions to the situations that arise, and she even started to protect her when the Demons and Heroes started coming after her; like her sister does. In volume XII, her and Mio have a threesome with Basara where Kurumi is shown to have adopted a sadistic and mischievous side, not unlike Maria. She gives Basara a pill while he is penetrating Mio that causes him to ejaculate five liters worth of semen into Mio causing her stomach to swell up, which was done to show how it felt when she and Maria got pregnant. Mio and Kurumi both marry Basara along with the rest of the girls in Volume XIII. The volume xiii final illustration show Kurumi fingering Mio, most likely meaning that they have developed a relationship similar to the one they both share with Maria in lewd scenarios.
Maria Naruse[]
Much like Mio, Kurumi and Maria started off as enemies in Volume II; however, they soon switched to a friendlier one. But, she soon became a plaything for Maria in a number of situations as Kurumi becomes the main victim in Maria's games using either her succubus powers or skills. However, the two of them do genuinely become friends as Kurumi finds herself accepting her feelings for Basara and fighting together along side her. Kurumi acts mischievous when Basara and Maria tie the vow in Vol XI, pushing Maria to make him penetrate her deeper. They become Basara wives along with the rest of the harem.
Zest[]
Kurumi started off having a very complex relationship toward Zest, due to the woman being mainly involved in the Zolgear Incident in kidnapping Mio, then attacking Basara, Yuki, and Maria. But, in Volume VI, due to the demons attempt to make amends for all that she did and she even assisted her in admitting her feelings to Basara, Kurumi became close friends with Zest. When the lingerie she is wearing activates an effect similar to the succubus curse, Basara begins performing lewd acts with the three of them, including nipping at Zest’s ears. When Zest begins giving Basara a paizuri, this incites her to give him oral after which Zest lets her perform the act. When Kurumi is beaten by Admirath, Zest intervened which led to her automatic disqualification.
Celis Reinhartd[]
As a child, Kurumi idolized Celis and admired her great strength and skills, viewing Celis as one of her most important childhood friends. In Volume XII, when she was feeling unsure about accepting her feelings for Basara, much like Maria and Zest, Kurumi assisted Celis in accepting her feelings, even not hesitating to assist her in climaxing after seeing Yuki and Basara engaging in sex.
Shiba Kyouichi[]
Although Kurumi and Shiba were partnered with one another in Volume II, she much like all the other Heroes has mixed feelings toward this hero due to the incident he caused. But, she didn't even hesitate to stand in front of him when he tried to "kill" Basara in Volume IX.
Hero Clan
Kaoru Nonaka[]
Kaoru is Kurumi's mother.
Shuuya Nonaka[]
Shuuya is Kurumi's father. He was worried for his daughter’s life when Shiba threatened them and the Hero Plan made plans to use them as sacrificial pawns. Later Shuuya, supports Kurumi living with Basara
The Elders[]
Takashi Hayase[]
They were partnered together on the mission to neautralize Mio, however Kurumi doesn’t share the same allegiance as she did after Basara saved her from falling.