Kiyotaka Ayanokōji/Relationships

Though Kiyotaka usually has trouble making friends, he has managed to gain some close associations and connections with some of his classmates which extends to those of other classes and even the Student Council. These are the known relationships of Kiyotaka with those who have truly interacted with him thus far.

Family
Not much is known about Kiyotaka's family, but according to himself, he was barely allowed to meet any of his relatives while in middle school. His father was said to be in charge of the White Room where Kiyotaka received his training as a child. Kiyotaka's father is also the only specific member of his family to be mentioned in the series so far.

Professor Ayanokōji
As Kiyotaka has not been seen interacting with his father, with only a few contextual fragments are known between the two. During the school cruise, his father contacted Sae, telling her to expel Kiyotaka for unknown reasons. Kiyotaka did not seem startled or surprised, most likely because he caught onto his father's involvement. However, he was very angry when Sae tried to blackmail him into reaching A-Class or face expulsion.

During the survival island test, he had reflected on his past once again and he remembered that an unnamed man telling him that only fools would waste their greatest talents. It was hinted that the mysterious man was really his father, due to the fact the man had a similar facial feature as him and was very familiar with him as he addressed him by his first name "Kiyotaka" rather than his last name "Ayanokōji". Also, this interaction with him may give a reason as to why Kiyotaka hides his true capabilities from others, giving him the motivation to do things without revealing his true talent.

After the survival test, Kiyotaka was told that it was indeed his father's wish to expel him and stated that Kiyotaka will soon pick expulsion out of his own will. Undeterred, Kiyotaka simply stated to Sae that he will continue to defy his father's wish by carrying on his usual school life the way he sees fit.

Suzune Horikita
Suzune was the first person that Kiyotaka interacted with entering the school. He first caught notice of her when they were on the bus witnessing Kikyo trying to persuade Rokusuke to move from his seat but to no avail.

They formally meet when she inquired as to why he was looking at her as he stated he saw a similarity between them in the bus incident. She told him not to compare them, as she chose not to involve herself in such a trivial matter as he noted that she's worse than him. They are later shocked to learn they are classmates, which Suzune stated was a bad coincidence after they seated alongside to each other.

After a few days, the two appeared to get along in class since they were both loners who barely associate with their classmates. In fact, it was noted by Kikyō that Kiyotaka is the only one in the entire class that Suzune interacted with. For that purpose, she tried asking him to help her befriend Suzune but failed. In response to his supposed connivance, Suzune forced Kiyotaka to aid her in reaching A-Class and though reluctant he complied after pressure was put on his choice.

Though technically forced to help her reach her goal, they appeared to be quite close as when he noticed her about to be assaulted by her brother Manabu, he quickly intervened on her behalf and demanded her to be let go. When she cried out for him to stop, he was surprised as he noted on the sincerity in her voice which he never saw in her. But before he complied, she soon witnessed him dodged Manabu's onslaught of attacks, leaving Suzune in awe. After her brother left hinting that Kiyotaka is more than he appeared to be, she herself inquired about him only to receive vague answers. In response, Kiyotaka asked Suzune if she ever considered her anti-social behavior was the reason she was placed in D-Class which left her unable to answer.

It seemed after all that, Suzune has started recognizing his talents as she immediately knew Kiyotaka had a hand helping the class pass the tests as opposed to Kikyō.

Suzune later asked him about his close association with Kikyō, noting in a rather tense tone at how he seemed more inclined to help her, but this only left him confused by her sudden change in behavior.

He helped her come back to her senses when she was scared by her brother's presence at Ken's hearing and she was able to give her speech. A day later, they work over the case with Ken by putting his accusers in a losing situation which forced them to withdraw their complaint. Despite Honami and Manabu believing he masterminded the plan, he told the people at the celebration party that Suzune was responsible for it. He soon met up with Suzune (who spoke to Sae about him) as they walked in the rain where she accused him of manipulating her and decided to ask about his motives and told him if he truly wanted to help her reach A-Class he'd have to be honest with her. He told her she forced it on him and that he may have gone along with it as he was just looking out for a friend, but she disregarded this as a lie pushing him to reveal his history, which caused him to briefly reflect on his life. He told her that he will help her reach her goal but sternly commanded her to not inquire about his history, marking the first time he was somewhat aggressive towards her.

Despite that conversation, they are shown to still be on good terms as Kiyotaka invited her to the pool, asking her to aid him in sabotaging the boys of their class from peeping on the girls during the summer break. Kiyotaka also tried to get her to loosen up by having her play with the students, though she still wondered why he hid his physical capabilities. While Kanji was stuck in the girls changing rooms, she gave a speech to distract everyone, helping him sneak out and while everyone was still in an awe. The former took the chance to stop the plan. Kiyotaka thanked her and tried again to get her to have fun by pushing her in the pool, which caused her to do the same in reply, and successfully got everyone else involved, accomplishing the goal.

Later that night, Kiyotaka sent Suzune a picture of her with the other students. His reason might be to show her that she actually can socialize with others and needs to open up a little more.

During the school survival test, Suzune asked Kiyotaka about his future but got no answer. After the panties incident, D-Class goes on alert and the girls asked for Yōsuke to keep an eye on the boys while moving from the camp, with Suzune making sure that Yōsuke is also watched by Kiyotaka, being put on guard duty as well. When he asked why she did this, Suzune stated she doesn't trust Yōsuke as he seemed secretive, which implied that she trusted Kiyotaka to a degree. Also, Kiyotaka discovered that she was sick and hiding it from the class, expressing concern for her health.

Later on in the test, he found Suzune injured after her fight with Mio and took her to a tree before she awoke. They talk where he discovered her reasons for wanting to reach A-Class and noticed she did want allies before imploring 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, D-Class won and she caught up with Kiyotaka and questioned on how the class won the test and unlike his other times; he told her his plan of outsmarting the other classes. His tactic and ingenuity left her in amazement at his intellect, she questioned as to what drove him since he didn't want to reach A-Class. He also gave her credit for the correct guessing of the other class leaders, much to her dismay.

In the anime, Suzune later caught up to Kiyotaka and confronted him once more as he calmly stated she needed allies as he noticed she finally changed her ways. After he confirmed that 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. However, it is revealed that Kiyotaka doesn't truly acknowledge her as an ally, but merely a pawn in helping him win.

Kikyō Kushida
She was one of the first people in his class to initially interact with and befriend him. His first impression of Kikyō is of her being a bubbly sweet girl who will be extremely popular in the class. He got along very well with her having no problem in playing part in her attempt to befriend Suzune.

She was surprised at how clever Kiyotaka was after he got the old test scores for the class and told her to take the credit for it since he didn't like drawing attention to himself. She seemed to be aware of his capabilities, as she asked Kiyotaka if he had anything to do with preventing Ken's expulsion, which caused everyone to stop their activities at the celebratory party to confirm it, but he passed the credit to Suzune.

He was surprised to see her violent personality wondering if that's who she really was. Kikyō threatened him with the false accusation of sexual harassment by putting his hand on her breast. She told him not to tell the tell their class about her secret which he promised to not expose as she went back to her bubbly-self, causing him to wonder which was her real self.

In Episode 4, he was shown to be a little uneasy about her as he was surprised to see her with Suzune and had a little problem in talking with her. When Honami inquired if they were together, Kikyō stated they were not as he told himself that's probably what she really thought of him. He also tried to stop her from asking Honami for help thinking it might be a prank, while Kikyō seemed curious about his relationship with Honami after she said that she owed him a favor.

In Episode 5, it was shown that while he is still able to hang out with her, he still has his doubts about her due to noting Airi's uneasiness about her, wondering if it was due to noticing that Kikyō was hiding something. His close association with Kikyō was questioned by Suzune, as she inquired as to why he is hesitant in doing a request for her, but all willing with Kikyō, to which he couldn't answer.

During the school cruise, he talked with her and noticed that her bubbly nature almost makes him forget about the more violent persona he saw in Episode 3. When he tried to leave, Kikyō stopped him, shifting back to her darker personality to make him talk with her. She inquired as to if he was nervous being alone around her, to which he confirms as she went back to her other personality, telling him that she just gets lonely when left alone. She appeared to want to tell him something, but backed out at the last minute and simply left.

After the survival test, they talk as she explained that she hates Suzune because of her supposedly not having a hidden side. She also asked if he had to choose between siding with her or Suzune and when he remarked he didn't know, she jokingly called him mean. However, it's revealed that Kiyotaka doesn't acknowledge her as an ally, but merely a pawn in helping him win.

Airi Sakura
Despite being classmates, the two don't take notice of each other until Suzune pointed out that she was the only person that could help Kikyō out. Kiyotaka reflected that he barely remembers her by appearance. They officially meet when Kiyotaka and Kikyō go to talk to her for help. However, Airi didn't want to get involved and ran off, leading to accidentally breaking her camera. She soon requested that he and Kikyō accompany her to get it fixed though he did ask her why he had to come before realizing her shy personality was something the flirty and pushy store clerk took advantage of. He helped her by telling the clerk to send him the notice for the camera as she looked at Kiyotaka while blushing. She later thanked him for this, as Kiyotaka simply told her not to act formally around him, since they were the same age and that he was just helping her out.

While Kikyō was away, he remarked to himself on how it was awkward to be alone with Airi who only stared at him. However, she broke the silence and asked him what she should do about Ken as he told her that the decision was up to her. He then asked why she wanted advice from him, with her replying that it was because his eyes weren't 'scary', causing Kiyotaka to be confused by her remark. He told her to do what she felt was right and that the decision Airi makes shouldn't have to burden her. Airi then blushed at his words and became flustered when Kikyō returned while trying to cover up her embarrassed face. Because of his inspiring words, Airi decided to help him in his case to save Ken from expulsion and went to the hearing and provided evidence for the incident.

After the hearing, Airi apologized to him for not working up the nerve to help out sooner, but he told her not to worry as she proved herself helpful. When Manabu hinted that a side of her could be lying, Airi got intimidated for a while, but Kiyotaka quickly intervened by saying he believed Airi, much to her relief. Despite Kiyotaka dodging Manabu's attack, she did appear worried for the former.

The day after, he met up with Airi in class and tells her that she was a big help. He then told her that if she ever needed him for anything he would be there, as Airi is touched by this and tried to ask him something, but he had to leave for something promising to hear it later. It is shown they exchanged contact information, as Airi soon made an urgent call to him asking for help. Although he seemed confused by the sound of her voice, he put two and two together to realize that she was in trouble. When the store clerk (who previously made advances on her) attempted to force himself on her, Kiyotaka quickly came to her aid by appearing on the scene and threatening the man with incriminating evidence as well as having Honami Ichinose and the police subdue him.

When Airi apologized for dragging him into the incident, he comforted her by replying it was not her fault. She decided to reinvent herself by embracing her status as an idol and discarded her glasses. He offered advice for her in any future burden she may face before helping her up, while she looked at him in surprise and blushed. These events and discussions led Airi to develop romantic feelings for him. It appeared that Kiyotaka is unaware of her romantic affections for him, though whether he felt any romantic affections for her or if he knows of her feelings is unknown. However, Kiyotaka considered Airi to be a very sweet girl due to their close interactions. He has the tendency to help Airi out and enjoys having her with him.

During summer break, it was mentioned that he invited her to the pool. They hung out by playing volleyball with the other students, seemingly having fun although Airi was nervous while interacting with others. Later, most of the students started splashing each other and she did the same to him but was seen nervous and slightly blushing after he looked at her. Catching a glimpse of him, his stare caused her to apologize and sink into the pool out of embarrassment.

On the cruise, Kiyotaka found Airi alone talking to herself, trying to practice her confession to him as he stopped to speak with her. To Airi's surprise, this led her to get flustered as she asked if he heard her. After confirming Kiyotaka didn't hear her earlier words, Airi is greatly relieved and instead asked him if he could help her in socializing with their class since she still had problems talking with them. When he agreed to help her, she becomes elated and grabbed his hand out of gratitude. However, this moment between the two ceased when Kikyō appears and Airi quickly excused herself. Kiyotaka was confused by her sudden change and looked on, wondering if she is still afraid of strangers.

During the survival test, she was paired up with Kiyotaka in a group and travelled through the forest with him. When they discover a spot, Kiyotaka has to hide Airi and cover her mouth after she tried moving ahead when Kōhei appeared. While being held tightly by him, Airi was shown heavily blushing full red before the coast was clear, even until Kiyotaka finally released her from his grip. He apologized for his sudden action, but Airi was seen still heavily blushing and squirming on the ground, as she nervously mumbled that it was fine, much to his confusion. Kiyotaka also asked her to come along with him, to look for branches for a campfire, after he initially requested help from Suzune who refused. Airi was seen staring at him blushing and made a sound gesture, sounding happy when he invited her, though Haruki was also seen deciding to tag along with the two of them. The group returned with an injured Mio Ibuki.

Later on, Airi explained that she was down on the school trip due to not having friends, but was now glad that she came. Airi then looked at him in an admiring way and stated regrettably that she wanted to have her camera so that she could take a great picture of him, which hinted that she probably thought that he would look good in a picture, as he was seen expressing confusion at her words.

On the final day of the survival test, Airi helped Kiyotaka clean up the campsite, where she asked him how many points that he thought their class was going to get. Kiyotaka then pondered on the topic and looked at Hirata afterwards. Due to his monologue at the end of the anime, is it unknown what he really thinks of her.

Kei Karuizawa
During the survival test, when Suzune selected Kiyotaka to serve as a guard along with Yōsuke Hirata to watch over the boys in the class, she noted on him being invisible to the rest of the class. Kei agreed with Suzune as he didn't seem lecherous to her, which seem to indicate that she doesn't take too much notice of him.

Due to his monologue at the end of the anime, it is unknown what he thinks of her.

Ken Sudō
Their first interactions involved Kiyotaka trying to get Ken to join Suzune's study group, but he initially turned it down. Kiyotaka later saw Ken when he was facing Kakeru and his men before Honami broke it up. He then stopped Ken from escalating the brawl even further before inviting him again to the study group, although Suzune had to convince him further to join

When the whole class passed the test, Ken is the only one who didn't get a passing grade and was at risk of being expelled, but Kiyotaka came to his aid along with Suzune by sacrificing 50,000 points each to prevent it. Later on, a celebratory party was thrown at Kiyotaka's room where Ken and his friends attend. When Kikyō hinted that Kiyotaka helped Ken out, everyone stopped their activities and looked to see if this was true but he passed the full credit to Suzune.

When Ken was accused of attacking students of C-Class, Kiyotaka decided to help prevent Ken's expulsion by enlisting aid from others, including Honami and Airi who both helped gather evidence.

In Episode 5, he is one of the few students who encountered the Student Council to help prove Ken's innocence in the fighting incident.

When C-Class withdrew their complaint against Ken, he happily informed Kiyotaka of this news. Once again, Kiyotaka hid his involvement in the act by congratulating Ken and giving Suzune the credit, leaving Ken to wonder if Suzune really did help. After the brief celebration, Ken left for practice as Kiyotaka looked on.

Due to his monologue at the end of the anime series, it is unsure what Kiyotaka thinks of their relationship.

Yōsuke Hirata
They first met when D-Class introduced themselves and Kiyotaka immediately guessed Hirata would be popular. Hirata also applauded him for making an effort in his introduction.

They didn't properly interact until the cruise, where Yōsuke tried to get Kiyotaka to become a mediator in getting Suzune Horikita to get on better terms with the class.

During the survival test, he and Yōsuke would work together in setting up camp. When Kei's underwear is stolen, Yōsuke searched the boys for them and Kiyotaka thought he might be caught as Yōsuke found them on him (after Kanji placed them on him). However, Yōsuke covered for him much to Kiyotaka's surprise. Kiyotaka asked why as Yōsuke revealed he knew that Kiyotaka wouldn't do such a thing. This implied he trusts him to a degree, despite barely knowing him.

After the survival test, it is revealed that Kiyotaka doesn't acknowledge Yōsuke as an ally, but merely a pawn in helping him win.

Teruhiko Yukimura
Teruhiko was briefly seen in the survival test, where he berated the girls heavily depending on points given to them. Kiyotaka recognized his intelligence in the survival test since he can accept a logical answer, especially when Kanji had sound reasoning for allowing the girls a proper toilet.

Other Classmates
Besides Suzune, Kikyō, Airi, Ken and Yōsuke, he does interact with his other classmates. In Episode 1, when the class introduced themselves, he tried to make a good impression but had a plain explanation that confused the other students. In Episode 2, Kiyotaka is downcast that everyone else made a friend while he was still alone. During Episode 3, a celebratory party is thrown in his room after a recent quiz and while he was happy he had friends around, he was concerned about the mess. He hid his involvement in preventing Ken's expulsion by giving Suzune credit for the plan after Kikyō mentioned that Kiyotaka had something to do with it. In Episode 4, he appeared to work well with his classmates as they all try to find evidence to prove Ken's innocence. When Honami offered to help out saying she owed him a favou, the group wondered why exactly someone so beautiful owed him. In Episode 7, Kiyotaka agreed to be part of the group of boys who wanted to peep on girls, although his real intentions were to stop them from getting their class in trouble. With Suzune's help, the plan was successfully foiled.

During the survival test, his lack of prominence in the class was brought into light when Suzune volunteered him as a guard after Kei's underwear was stolen, causing a few of them to agree with the statement. However, a majority agreed to put him on guard duty because he didn't look lecherous like the other boys in the class.

Due to his real thoughts, it is unknown what really thinks of his classmates. However, it seems his actions help them out in the long run as shown in the survival test where the class won, but he covered his tracks by giving Suzune the credit.

Mio Ibuki
Kiyotaka first met Mio on the school cruise where he witnessed her being knocked down by Albert after being shunned by Kakeru. He went to help her up but she angrily slapped away his hand telling him to stay out of her business before running off. He noticed with this exchange that Class C was falling apart.

They met again in the survival test where he found her injured in the forest. Kiyotaka even found himself stopping Haruki from approaching Mio at first because of how suspicious the situation was. He later said it was nothing as they let her come to their camp. Though Ibuki refused help from an enemy class, she accepted the offer and returned to their camp, but made it clear she isn't trying to be friendly with them.

On the day after Kei's underwear is stolen, he is approached by Mio who asked if he believed she was responsible for the underwear theft since she was an outsider, but he replied that he knew she didn't do it. He stated that while the other students in his class don't trust her, he does which led to her nervously thank him for having belief in her as he said he was just being honest. She was curious about him, glancing from behind when Kikyō and Haruki commented on how incredibly close Suzune and Kiyotaka were.

After the survival test, it was revealed that Kiyotaka knew Mio was really a spy and he outsmarted and manipulated her by using various tactics which helped his class pass the test.

Kakeru Ryūen
No direct interaction was made in the anime, although they saw each other face to face in the survival test. Kakeru did not appear to think much of Kiyotaka, while the latter took note of former's camp. He soon realized Kakeru's plan and foiled it brilliantly and flawlessly.

Other C-Class students
Kiyotaka met a few of them during their attempts to frame Ken and foiled their plans with help from B-Class, Suzune and Airi.

Honami Ichinose
Kiyotaka had first met Honami when she passed by the school store after Kikyō stated they had already become friends. He later watched her prevent Ken from getting into further trouble with Kakeru Ryūen and his classmates in C-Class.

They met formally at the dorm ground floor where he and Kikyō bumped into Honami, who asked Kikyō if she was dating Kiyotaka, but is told that wasn't the case. Honami later called on him and begged him for aid by asking him to pretend to be her boyfriend after one of her friends gave her a love letter. This showed in spite of just meeting him, she trusted him to an extent as she could have chosen anyone. When he initially refused, she continually begged for advice saying she didn't know how to handle it before her admirer showed up. When asked what kind of relationship they had, Honami tried to nervously "confirm" that they were a couple, but Kiyotaka immediately interrupted by saying that he and she were simply friends. Both girls were surprised by his bold statement. He left Honami, telling her to talk it out with her friend due to the courage she mustered up to confess. She was amazed by his wisdom and proceeded on by deciding to follow his advice. This event showed he has no problems associating with her and is willing to help her. Whether he truly sees her as a friend is yet to be revealed.

After Honami turned down Chihiro, she thanked Kiyotaka for helping her out and apologized for dragging him into her mess, though he was fine with it as Honami smiled and stated she owed him for his help. She later offered to help him and his class in proving the innocence of Ken. She stated that her intentions are pure and slyly winked at him after she reminded of the debt she owed him, while he simply gave a blank but understanding expression. This display got attention from Kikyō and the other male students who wondered exactly what an attractive girl like Honami owed Kiyotaka.

Honami acted on her word as she helped him gather evidence for the case that may help in the investigation. Kiyotaka noticed she had no problem trusting him after she let him borrow her phone before seeing how many points she had and seemed curious that she amassed such large points until she took back her phone, but still promised to help in the future.

He soon requested her aid by borrowing points from her to use cameras that would cause C-Class to withdraw their complaints. Afterwards, he spoke to her to pay her back for the help as Honami expressed amazement at his intelligence and started questioning why he was placed in D-Class but got a vague answer in response. She noticed his uncomfortable attitude and simply smiled in response, probably out of consideration for his privacy. The two later worked together in saving Airi from a crazed stalker who attempted to force himself on her. This interaction would suggest they are indeed friends since she was willing to help him save Airi though she had no obligation to help.

They later hung out at the pool where they had fun with their classmates.

Unknown to him, while on the cruise, Honami spoke with her homeroom teacher, Chie, about his intelligence and was curious enough as to why he hides his talent.

In the survival test, Honami showed him and Suzune around the camp before giving them supplies for their camp. After that when he and Airi went to the camp for C-Class, he asked her about Kōhei Katsuragi and Arisu Sakayanagi with Honami giving him information on the leaders of A-Class.

Due to his monologue at the end of the series, we don't know his real thoughts towards her though he seems to consider her as a valuable associate as they get along well. In the survival test, he took their class alliance into consideration when naming the other class leaders.

Arisu Sakayanagi
No direct interaction has been seen and established yet between the two in the anime. During the survival test, he asked Honami about Arisu and learnt of her prominent stature in the school.

Manabu Horikita
Kiyotaka first saw Manabu give a speech at the first year students' entry ceremony and soon wondered if he was related to Suzune after hearing they have the same last name.

They had their first encounter when he found Manabu about to assault his sister Suzune but quickly intervened by grabbing Manabu's hand, admonishing him for his actions before telling him to release Suzune despite her begging for him not to get involved. He complied but Manabu unleashed his fury by assaulting Kiyotaka, who responded by dodging all his attacks and gained Manabu's respect. Impressed, Manabu questioned Kiyotaka over the fighting style that he practised only to receive a vague answer before recalling Kiyotaka as the student who scored half the total score on his entrance exams and his recent quiz. He then inquired about this, hinting that Kiyotaka was hiding his intelligence on purpose, but the latter shrugged this off.

They met again by both being present at Ken's case. It was shown that Manabu had expectations for Kiyotaka, stating that he believed Kiyotaka's presence at the hearing meant that he had a strategy, but his question was disregarded. Manabu attempted to attack Kiyotaka again, but the latter dodged his strike and Manabu questioned again if he has something planned. Again he received a vague answer

When C-Class's complaint against Ken is withdrawn, Kiyotaka met with Manabu and his secretary, Akane, in the hallway. He talked to him about the event before congratulating him on his victory, but Kiyotaka once again gave Suzune all credit for the act. Glaring at Kiyotaka, Manabu asked Tachibana if they had an opening on the secretary post of Student Council, which she confirmed. Manabu offered the position to Kiyotaka, showing that he truly saw him worthy of a higher status. Kiyotaka turned down the offer in favour of living a normal school life. Manabu conceded by accepting his decision for now.

Sae Chabashira
Sae is his homeroom teacher and didn't personally interact with her in the first few episodes. After a class test, he convinced her to halt the expulsion of Ken by offering her points. Having learnt it was within the rules, Sae is amused by his offer and demanded a sum that will require nearly all his points, but his efforts were aided by Suzune, who offered to pay half the sum. Sae was amused by their actions as it was something that has never happened in the school and relented in expelling Ken, telling the two to continue in making things interesting for her. Unknown to Kiyotaka, she has an opinion of him being the most "defective" of the class as he has extreme intelligence and talent that he keeps secret from others but placed in the lowest class instead of the higher classes he could've placed in.

During the school cruise, Sae talked to Kiyotaka, informing him of an unknown man who wanted to expel him. She promised to protect him, but only if he will start working to reach A-Class. However, Kiyotaka refused to comply with this as she promised that he will be expelled, leading him to grab her by the collar in a threatening manner to get her to back off and warn her not to manipulate him or else she will regret her actions. This was remarkable as he never usually resorts to physical threats. It's currently unknown why she wanted him to advance to A-Class. Her reason might because she felt he is wasting his talents and that he is better suited for the upper classes.

After the survival test, Sae summoned him to the theatre where she commended him on his victory over the other classes and revealed that it was indeed his father who had made the request to expel him. Once again, he refused her demand to advance to A-Class which she doesn't protest like last time. Instead, she simply laughed and revealed her knowledge of his past after he stated he won't do anything for her without proof. Sae then asked him what he plans to do now, to which he gave her a vague answer, leaving her smiling in response.

Chie Hoshinomiya
Despite not having any interaction in the anime, it appears that Chie has suspicions about his intelligence, as while talking with Honami, she recognized him as a person from D-Class to watch out for the most.

White Room
As a young child, Kiyotaka was a part of this unknown organization, which greatly contributed to his vast and extreme intellect, talents and skills. In a flashback on Episode 10, it can be seen that he was taking an examination, that can be considered as extremely and immensely challenging, let alone, heavily advanced for a young child. This emphasized and proved that he had an extremely advanced upbringing, which could explain his vast and extreme intellect, giving him very high mental prowess. It is also assumed that he not only underwent heavy mental training there but also went through a very intense physical regime, such as studying martial arts and learning various self-defence techniques, giving him a very high physical prowess. However, it is unknown what his experience there was like and whether he had any friends. Later on, it was shown that Kiyotaka gets very angry towards any subject concerning his past. As shown in his talk with Suzune in Episode 6, where he sternly warned her not to pry into his past ever again.

It appears he picked up the belief that winning is everything from the place and doesn't hesitate to use people as a means to do so. This harsh upbringing would likely explain why he speaks in a monotonous way to cover up his feelings.