Manabu is her older brother as well as the student council president. Suzune is shown to admire and wants to prove herself in his eyes but because of her status as a student in Class D, she is seen as nothing more than an embarrassment to him. Despite her respect for him, she holds some resentment towards him as she got irritated when Ayanokōji asked if they were related but Suzune's glare prevented him from broaching the subject. However, this also could be because she doesn't want to answer any personal questions regarding her life and may not resent her brother.
She goes to talk with him and he is distant towards her due to her position in the lowest class while she tries to nervously talk to him which is a contrast to her composed and serious behavior. After she says it's not her fault for being placed in Class D and she will reach Class A, he angrily grabs her and lists all the shame she has brought to his and their family's name. He then demands her to leave the school while she is showing scared, marking the first time she showed fear. She tries to state her plan to ascend but he did not accept this excuse and tried to assault her until Kiyotaka intervened.
After a brief skirmish, Manabu voiced his surprise that she made a friend and derided her words after she said that it was not the case before he left his shaken sister with advice to move up.
She is seen nervous at his presence at the hearing for Ken Sudō and is unable to speak until Ayanokōji tickles her and she regains her resolve. Despite her strong speech and determination in the case, Manabu is not impressed and continues to not expect anything more from her.
It is shown that in spite of their turbulent relationship that Suzune keeps a portrait of herself and her brother in her room, showing at one point they were close. During the summer outing, though they didn't interact personally, Manabu bore witness to his sister's speech of how its possible for Class D to reach Class A. After the speech, his only reaction was a glare at his sister who responded in the same way, its unknown what he thinks of her now.
During the survival test, Suzune reveals to Kiyotaka that her reasons for reaching for Class A was so her brother would acknowledge her talents.
Class D Edit
Suzune is the first person that Kiyotaka interacts with when entering the school. He first caught notice of her when they were on the bus after they witnessed Kikyō Kushida trying to persuade Rokusuke Kōenji to move from his seat to no avail.
They formally meet when she inquires as to why he was looking at her as he stated he saw a similarity between them in the bus incident. She tells him not to compare them as she chooses not to involve herself in such trivial manner as he notes she is worse than him. They are later shocked to learn they are classmates which Suzune states was a bad coincidence after they seated next to each other.
After a few days in class, they appear to get along well since they are both loners who barely associate with their classmates. It was noted by Kikyō that Kiyotaka is the only person in the class that Suzune interacts with at all and she tried asking him to help her befriend Suzune but it failed. In response to his supposed conspiring, Suzune forced Kiyotaka to aid her in reaching Class A and though hesitant he complies after she puts pressure on his choice. It is unknown why she picked him but she may have saw his insight and wisdom would be a reason to help her in achieving her ascension to Class A.
Though she forced him to help her reach her goal, they appear quite close as when he notices her about to be assaulted by her brother Manabu Horikita, he quickly intervenes on her behalf. When she cries out to him to stop, he notes on the sincerity in her voice which he never saw in her while she watches in awe at him nimbly avoiding her brother's attack. Manabu even states he was surprised to see that she made a friend but she states Kiyotaka was just a classmate of hers. After her brother hints that Kiyotaka is more than he appears to be, she herself begins to inquire about him only to receive vague answers, calling him strange. Also a comment from him about her distant ways most likely caused her to ponder on how she does things as she appeared deep in thought on whether she was holding herself back.
It seems after this event, she recognizes Kiyotaka's talents as she immediately knew he had a hand in giving the test scores to the class rather than Kikyō and questioned him over his actions but he doesn't give her a clear answer.
While she merely sees him as means to enter Class A, she later asked him about his close association with Kikyō, noting he seemed more inclined to help her but is hesitant with her leaving him unable to answer. Her tone of voice hints at some irritation at his time spent with Kushida.
During the hearing for Sudō, when she is unable to speak out of fear from her brother's presence, Kiyotaka tickles her which brings her back to her senses and she is able to give her speech without problems.
She later has him aid her in her in goal to save Ken Sudō and they are successful in forcing Class C to withdraw their complaint with both using impressive tactics to do so. Afterwards, she goes to talk with Sae Chabashira, who says there is more to Kiyotaka that meets the eye and the talk causes Suzune to question the mysteries about him and whether she really can trust him. Suzune meets him in the hall and the two would walk together in the rain where she accuses him of manipulating her so that she would force Class C to withdraw their complaint. This leads her to question him about his motives since he promised to help her reach Class A as he answers that was because she forced him to and tries to leave. She stops him and questions him even more about himself if he expects her to trust him. When he tries to answer by stating he is just looking out for a friend, she disregards this as a lie pushing him to reveal his history. In response, he tells her that he will help her reach her goal but sternly tells her to not inquire about his life, marking the first time he ever got serious with her.
Despite this little turbulence, they are shown to still be on good terms as Kiyotaka invited her to the pool (which she refused at first) where he asked her to aid him in stopping the boys of their class from peeping on the girls during the summer break. When some of the girls discussed their associations with Kiyotaka, Kikyō had told Suzune to be careful as she voices that she has no interest in whoever Kiyotaka befriended. Kiyotaka also tried to get her to loosen up by having her play with the students though she also wondered why he hid his physical capabilities. Later on, she helped him in stopping the other boys' plans of peeping by giving a speech to distract everyone. He thanks her and tries again to get her to shake off her strict nature by pushing her in the pool which causes her to do the same to him but this act somewhat works as it gets her to play with the other students.
Later that night, Kiyotaka sends Suzune an email which is a picture of her with the other students as she remarks on how she gets along fine without others but smiles at the gesture.
During the school survival test, they spend time together and Suzune asks Kiyotaka about his future but gets no answer. When panties are stolen, Class D goes on alert and when the girls ask for Yōsuke Hirata to keep an eye on the boys. Suzune had no problem with this but makes sure that Yōsuke is also watched by putting Kiyotaka on guard as well since he is not lecherous like the other boys. Her decision was met with some initial protest since Kiyotaka isn't prominent in the class but it is soon agreed too.
When he finishes working, she approaches him and he asked why did she make him a guard, as Suzune states she doesn't trust Yōsuke as he seemed like a secretive person with a different side to him. While she said the same went for Kiyotaka as well, her reason for making him a guard implied that she trusted Kiyotaka to a degree. Also, she blushed when he put his hand on her forehead after finding out she was sick and hiding it from the class. She was shocked when she deduced that he was responsible for burning the survival manual and wondered why he did it.
After the survival test, he found unconscious Suzune injured after her fight with Ibuki and took her to a tree before she awoke. They talk where she confided in him of her reasons for reaching Class A and admitted she wanted allies before he implored her to withdraw from the test but she refused out of pride though she fell unconscious forcing him to carry her and have her withdraw due to her ailing health. After the test, she was surprised the class had passed the survival test and immediately suspected he had a hand in it. She met up with him and questioned him on how the class passed the test and he tells her his plan and how he outsmarted the other classes with various tactics, which leaves her in amazement at his intellect. She soon inquired on what drives him since he had no intention of reaching Class A. She was also surprised that he gave her credit for the correct guessing of the other class leaders, much to her dismay.
She also caught up to him and confronted once more as he calmly stated she needed allies and noticed she finally changed. After he confirms he did everything to help her, she got flustered and blushed before begrudgingly thanking him as she stated she will see him as an ally. This shows she has come to respect him since he has helped her in both overcoming her social shortcomings and when she is unable to complete a task.
In the light novel, their relationship is more or less similar to the one in the anime as he tries to befriend her but is rejected due to her personality.
Because of her goal to be friends with everyone, Kikyō has tried to extend this to Suzune but fails in the end due to the latter's disinterest in friendship. Kikyō once tried to enlist Ayanokōji since he was the only person that Suzune spoke to everyday. Kikyō explained her plan was to meet with Suzune and be friends though Suzune saw right through it and rejected the offer once again.
Unknown to Suzune, Kikyō harbors great contempt for her cruel and antisocial ways as shown in Episode 3 where Ayanokōji finds her throwing a tantrum and cursing Suzune's name. However, she appears to want to hide this revelation from others as shown when she threatened Ayanokōji to keep quiet about the incident.
It appears that Suzune is somewhat aware of Kikyō's contempt for her, as she reflected on the look Kikyō gave her and wondered why she would associate with her if she possesses dislike for her. Despite that, they are seen talking civilly, as they discussed the friendships that Ayanokōji has made with several girls and it seems that Kikyō believes Suzune has affections for Ayanokōji as she teased her but the latter shrugged it off. They are later seen playing in the pool splashing each other after Ayanokōji and Suzune threw one another in the pool.
During the survival test, Kikyō acknowledged Suzune's talents and made her leader of Class D as it would be unexpected for the other classes. Suzune was surprised by Kikyō's request followed through with the suggestion becoming the class leader.
They have a rocky standing due to Suzune's habit of speaking her mind and not being afraid to hurt people's feelings with blunt words which only serves to provoke Ken's quick violent temper. In Episode 2, she implored Kiyotaka to convince Ken to join her study group but he refuses and goes to basketball practice. Suzune was not done with him as she personally goes down there and makes him think about his athletic career and how it would be at stake if he were to be expelled which persuaded him to go study. However, Suzune's blunt personality got the better of him and he voiced that he didn't join just to be insulted but she wasn't bothered. When Kikyō gave everyone old test exams to help everyone, they all got passing scores except Sudō. In Episode 3, because of his failure, Ken was nearly expelled from the school but this action was stopped when Suzune and Kiyotaka sacrificed some of their points to stop it which the teacher accepted. The two later attended at a celebration party at Kiyotaka's room which was attended by several other classmates as well. When Kikyō hinted that Kiyotaka helped Ken out, the latter and the others stop their activities and looked to see if this was true but he casts the credit to Suzune. A startled Suzune was barely able to explain to a curious Ken that she did it for her own benefit.
In Episode 5, she helps him in a case to prove his innocence after he is accused of fighting three students. Initially, Suzune struggled to say anything (due to her brother's presence) but with help of Kiyotaka she was able to speak on Ken's behalf. She began her speech with criticism of his character which angered him at first but she stated he was not at fault for this incident, to his shock. Ken watched as Suzune used her charismatic words to bring evidence that he was not at fault first by pointing out holes in Class C's story and by bringing in Airi Sakura who had pictures of the incident. When those representing Class C protested, Suzune stated she would not accept any compromises and wanted to dismiss the accusations towards Ken who sat staring in admiration of her abilities.
In Episode 6, when Class C withdrew their complaint against him Sudō informed Kiyotaka of this (not knowing he aided in this act). Kiyotaka congratulated him on this and when the relieved Ken wondered Suzune did something to help him, Kiyotaka again gave her the credit. After the brief celebration, Ken called Suzune amazing for her actions before he left for practice as Kiyotaka looked on.
They hung out with another during summer break and after Kiyotaka threw Suzune in the pool to get her to have fun. Ken and the others thinking they were playing a game, joined in and started splashing Suzune.
In Episode 8, it is hinted that despite their previous hostile interactions, Ken might have developed romantic feelings for her due to his excitement after he was told her first name, calling it cute, repeatedly.
Other Classmates Edit
Suzune is insulted that she was placed in a class full of the school's idiots. She does not try to get friendly with anyone except Kiyotaka Ayanokōji, and is rather distant towards her other classmates, which has given them the impression of her being cold-hearted and uncaring. She also interacts well with Airi Sakura as she worked with her in stopping Sudō's expulsion and thanked for her help. Some of the class acknowledge Suzune's intelligence and many have tried to befriend her but her disdain for friendship causes her to keep them at arm's length.
During a confrontation with Mio Ibuki, she acknowledges her previous views of the class and saw that she was no better than in having to resort to violence.
After the survival test, it turned out Ayanokōji made it appear that she was the one responsible for class D's victory in order to have others put their trust in her. As the class thanks Suzune, she is nervous and flustered by their attention as she tries to explain what really happened but to no avail.
Is her teacher, they didn't interact very much until Suzune offered to help Ayanokōji to pay for stopping Sudō's expulsion. Chabashira was amused by this and accepted their payment and tells them not to disappoint her since they did something nobody in the history of Class D has done. It appears after this she has become interested in Suzune after she told her that she intends to ascend to Class A stating those with defects can overcome them and advance.
Following Sudō's fight with Class C, Suzune later went to talk with her teacher after she called her up. Chabashira had inquired as to how Suzune had got the other class to withdraw their statement but was given no answer so the teacher instead told her to understand Ayanokōji better as she needed to know the "defective" traits of those around her and his was that he hides his amazing talents. Chabashira's words later caused Suzune to have a talk with Ayanokōji about his past and why he chooses not to elaborate on himself.
Class B Edit
They barely had any interaction but in Episode 7 they hung out at the pool during summer break. During changing, Suzune questioned Honami over her chest size as the latter was somewhat embarrassed on answering. Suzune also agreed with Kikyō's comment of Honami being close to Kiyotaka as the latter smiled. Like with others, Suzune appears to have studied Honami's personality and behavior which described her as intelligent, talented, and kind which meant she recognized her capabilities.
They met again in the survival test and Suzune was impressed by Honami's way of leading her class.
Class C Edit
No direct interaction had been made in episode 6, though Suzune played a role in stopping his plans of getting Ken expelled. In Episode 7, he spots her giving a speech to everyone at the pool recalling her as the girl who foiled his plans.
They formally met on the school's cruise ship in Episode 8, Kakeru found Suzune, sitting at the bar, and addressed her by the first name, giving hints that he is aware of what she did to get the complaint withdrawn. Suzune, who seemed to be very disgusted by his presence, found his arrogant attitude off-putting and told him to keep away from her but he responded by taking a picture of both her and Kiyotaka, after claiming to be a fan of her and stating he had already made plans to take care of her personally, he tells her to look forward to it.
In Episode 10, he was seen flirting and was persistent on make advances on Suzune, as she and Kiyotaka were scouting class 1-C, stating that he will prepare a special tent just for the two of them, as well as, make her taste real heaven, where she glanced back at him presumably creeped out, disgusted and probably freaked out. Then after that, she is seen leaving with Kiyotaka, stating that being there any longer than they should have will just make her even iller.
Not much is known about their relationship, but it seems that they have a rivalry relation going on.
In the survival test, Suzune was seen, after she was reprimanding Mio for stealing the key card, fighting Mio, who easily overpowered her due to Suzune's own illness and her inability to defend herself against Mio, causing the latter to defeat her.