Arisu Sakayanagi

Appearance
Arisu is a petite teenage girl with lilac colored hair and violet eyes. She wears a black beret on her head with a gray ribbon connected to it and wears the standard school uniform.

She often walks with a cane due to her health condition and she is quite short for her age when comparing to other classmates due to her at birth.

Personality
Arisu appears to possess a "go with the flow" attitude as she accepts most situations with no protest. Although she voices her dislike of boring situations after Kōhei Katsuragi (Arisu's classmate) spoke about the class scores. Unlike Katsuragi, who has a conservative stance, Arisu possesses an innovative outlook on things. Together, the pair effectively lead class A through the school years.

She enjoys situations she finds interesting as shown when she smiled at Kakeru Ryūen's declaration to rule the school or when she listened to the speech of Suzune Horikita.

In the light novels, Arisu enjoys toying with people, as seen when she cryptically hinted that she knew Kiyotaka Ayanokōji, whereas he doesn't remember meeting her before. Later on, while being together with Honami Ichinose, she also appeared to be very confident and complacent after Teruhiko Yukimura of Ayanokōji Group boldly claimed that D-Class has a plan to overtake A-Class soon.

Additionally, although she has an easygoing personality, it was shown in the latter part of the series that she is easily provoked when being described based on her petite appearance (e.g. "Little Girl"), as she believes that it does not give her justice, due to her domineering qualities.

Plot
Arisu is introduced in the anime when she and Kōhei Katsuragi were being talked to by the Student Council President about the school system.

After a while, she is seen next to Katsuragi in the hallway while observing the class points of each class. She then proceeded on commenting on how things get very boring due to seemingly no struggle between the groups.

One day, while out in the rain she and her followers meet Kakeru Ryūen and his followers. While her group protectively surrounds her, she stops them, stating to Ryūen who remarked on how it looked like that she had established her rule in the school very quickly. He swore to her that he will take down all the classes including hers so that he could rule the school. She simply smiled at his declaration, remarking how he was making things interesting for her, before agreeing with his previous statement.

In her short story, Arisu was reminiscing about the sports festival, more specifically dreaming about Kiyotaka Ayanokōji, with his race against Manabu Horikita, the student council president himself. She revealed that from her point of view, Kiyotaka was way faster than Manabu during that race (only reason Kiyotaka lost the race was that one of the other participants incidentally tripped and got to Kiyotaka's lane, causing Kiyotaka to lose the race by changing his track). After her monologue, she awakens and says that she wants him while wondering why he came to the school in the first place and questioned his reasons for being in D-Class. It didn't bother her if she ends up being his enemy one day. She began to enter a long discussion with Katsuragi, about their competition with B-Class, she then mentions how she initially thought Ryūen was going to make things interested for her — that was until she reunited with Kiyotaka. Arisu then asks Masumi to watch Kiyotaka closely and reveals how much he has grown since the last time she saw him and that she will enjoy what happens next.

Later in the series, Arisu became acquainted with Honami Ichinose. As they walked together, they briefly met Ayanokōji Group and talked about how D-Class is fairing greatly with the recent test, Paper Shuffle, and it massively damaged C-Class' standing. Arisu stated that during the same test, both classes A and B sustained scores whose difference is reasonably insignificant, thus, concluding that the said class must have the same average intellectual abilities. Ichinose, then, teasingly stated that if her class doesn't put their guards up, surely, D-Class will take their throne. Teruhiko Yukimura made a snarky remark that not only Ichinose's class will be targeted, but also, Arisu's. After he summoned his bold instance, an awkward scenery came in between among all of them driving Arisu to laugh lightly to ease the situation. Ichinose observed the Ayanokōji Group members' body language — that they might be feeling too uncomfortable to the two of them, so they bid goodbye to the group.

Afterwards, Arisu is seen interfering with Ryūen's interrogation of Rokusuke Kōenji. Following a long argument between the two leaders, the dialogue ended on them discussing the identity of "X". Just as before Rokusuke is about to tell his thoughts, Arisu immediately stated that there is a possibility that "X" doesn't exist and that Suzune Horikita should be at the watchlist given that she's the one who manipulated the settings during the special summer exam at the deserted island.

The scene proceeded with Arisu being saved by Masayoshi Hashimoto after Ryūen violently assailed her for repeating Rokusuke's embarrassing nickname for him (e.g. "Dragon Boy"). After this, Rokusuke made a degrading nickname for Arisu (e.g. "Little Girl") which provoked her into proving that his naming sense doesn't give justice to the name-holder. The scene ended with Rokusuke stating that his thinking is beyond the justice of common sense and no one is allowed to interpose with whatever he wanted to say.

During the winter holidays, Arisu runs into Kiyotaka and they decide to talk a little, she reveals to him that she already heard about Ryūen stepping down as leader, considering only 1 day has passed since the incident at the rooftop, Arisu's network of information seems to be extremely efficient. Arisu asks Kiyotaka if he was the one who defeated Ryūen although he denies that he had any involvement in that situation she doesn't press any further. Instead she says that she felt left out due to class D and C having their own battles that she wanted to find an opponent for her own, having decided on Ichinose. Arisu tells him that she plans to attack her at the start of the next term, and that if she were to disappear, she might have no choice but to find other targets to destroy. At this point Kiyotaka tries to get her to focus her attention on Ichinose by revealing that he wonders if she is good enough to destroy her since she perhaps got into class A because her father was the director of the school. Arisu doesn't like his provocation. As they are talking, Kamuro comes looking for Arisu as they are talking, telling her not to disappear from their arranged meeting place like that. With Kamuro here they start talking about whether Ichinose really is a good person, and she reveals a little about Ichinose's secret to Kiyotaka and Kamuro saying that the secret Ichinose keeps is the same as the one Arisu uses to control Kamuro. Kiyotaka asks why Ichinose would tell her something like that when she says Ichinose told her about it herself, she says she obtained the information via cold reading. With her warning given, Arisu and Kamuro go off to hang out together.

Arisu is participating in the Mixed Training Camp while nothing much happens among the first years, an incident where Haruki Yamauchi bumps into her causing her to fall down is the stage for her future plans. Yamauchi who is not the most sensitive person, offends Arisu with his attitude. Which Kiyotaka who watches the scene unfold notices when he tells her Yamauchi didn't mean it, Arisu says she understands that but her face shows a much darker emotion. Before they part ways, Arisu once again asks Kiyotaka if class B can trust Ichinose as their bank although Kiyotaka replies that that should be up to Ichinose's class to decide.

After the mixed training camp as the winter term begins, Arisu begins her attack on Ichinose. She starts by spreading rumours about her through the class A students before spread towards the whole school. The rumours being spread are: 'A History of Violence', 'Engaged in Compensated dating', 'Engaged in theft and robbery' and 'A history of drug abuse'. While Ichinose deals with these rumours by ignoring them, which Arisu expected because by having a truth spread among the rumours, if Ichinose were to complain to the school, her past would be revealed as a result. After a few days, it appears as though there are no truth to the rumours as Ichinose successfully ignores them. However, Arisu continues her attack by using post boxes of the students with a letter revealing that Ichinose is a criminal. This attack seems to have a mental effect of Ichinose who becomes a shut in after seeing the letter. On the day she sends the letter, she also sends Kamuro to go and tell Kiyotaka about what Ichinose's secret is.

Arisu also one day appears in the class C classroom looking for Yamauchi hoping to talk to him. They go and talk outside the classroom where she appears to be fiddling her hair like a girl trying to appeal to the guy she likes. As there are multiple students watching them, she asks if they can go somewhere more private.

On the day, that Ichinose finally returns to school, Arisu takes her faction with her to visit the class B classroom to continue her attack, revealing Ichinose's past herself saying that she is a thief and that her class should not trust her with their money. In response, Ichinose reveals the whole truth to everyone present and offers to step down as leader of class B but her classmates do not want her to do that so she says she will continue working for the good of the class. Sakayanagi seemingly angry, tells class B that a crime is a crime and that they shouldn't be so quick to trust her again seeing as that is not working, she proceeds to say she will continue her attacks but the school staff arrives and says that slander and rumours will no more be ignored by the school since more students have been affected and complained, due to the rumours that Kiyotaka himself chose to spread. With that she leaves the class.

When that is over, she calls Kiyotaka and asks to talk to him. She firsts asks why he helped Ichinose, as the rest of the questions she had she could figure out herself. Kiyotaka returns the question by saying that's what she wanted by sending Kamuro. Telling her that he knew it was her plan for him to help her as a way to challenge with in the background, although Arisu denies this at first she asks why he thinks that. He tells her that the beer can Kamuro had passed to him had an expiry date far to old to be have just been stolen which means it was the beer can that Arisu had caught Kamuro stealing at the start of their school year. In order words, it was her plan to have Kamuro reveal the secret to him. Arisu is impressed that he saw through all of it and says that he is an enemy worth defeating. She challenges him to face her lightly threatening to expose him if he doesn't although Kiyotaka thinks she won't do that either. Kiyotaka eventually agrees to face her in the next special exam with her expulsion on the line as a means to remove her so she won't be able to reveal his past.

On the first day of the supplementary |Class Poll special exam, Arisu and Kamuro happen to meet Kiyotaka. They discuss about the current exam saying that it seems very unreasonable, with Arisu revealing that her father the director has been removed from his post by dirty tactics which may explain why the exam is so different from previous exams. Arisu asks Kamuro if she wonders why she is so interested in Kiyotaka, Kamuro says she is. Arisu replies that they knew each other from before coming to this school. Kamuro wonders if Kiyotaka is even a worthy opponent as she can't see that at all. She then tells Kamuro to leave so that she can talk to Kiyotaka to discuss their deal. She tells him that this exam isn't suited for their battle, so she wants to postpone it to the next exam. Seeing no reason to disagree, Kiyotaka agrees with her idea. She even gives him a verbal agreement that she will take no actions that will harm him in this exam at all. Kiyotaka wonders who she will expel from her class, and she tells him it's already been decided to be Katsuragi.

Before they happened to meet Kiyotaka, Arisu had made plans to meet with Yamauchi that night, Kamuro is curious as she noticed that Arisu had seen her contact with more often recently. She asks if Arisu actually likes him, but she reveals she has just been training a spy in class C and this exam is the perfect exam to test who usual he is. They meet in the karaoke room, Arisu brings Kamuro along for the date saying that she is too embarrassed to go on a date with just the 2 of them. She tells him that she wouldn't want to see Yamauchi expelled so if he needs help he should as her. Arisu tells him that he should target a student on one would miss and Kamuro seeing her plan offers Kiyotaka as a sacrifice. Yamauchi is afraid targeting someone will make him the target so Arisu offers 20 of her classes praise votes in case so that he won't be expelled. When Yamauchi leaves, Arisu and Kamuro discuss how strong Kiyotaka really is, Arisu says no other class leader like Katsuragi, Ichinose or Ryūen has a chance but for her she says she can win. However, a part of her wants to be able to lose to him. Wondering how strong he really is, and hoping to see it when he is going to be expelled by her hands.

After a day goes by in the class poll exam, Yamauchi has amassed enough about half the class to vote on Kiyotaka due to Kushida's help. On Friday the day before the exam, Yamauchi tells Arisu that he has been exposed as the ring leader and is being targeted, he calls wanting to confirm that he will receive her classes praise votes. She promises that she will. Hashimoto had previously advised her to not include Kei Karuizawa in the students targeting Kiyotaka but she did it anyone but staggered the timing making sure to only include her on Thursday to make sure she would know if Kei was really helping Kiyotaka in the background, since Kiyotaka made his move on Friday, it confirms the suspicions. Hashimoto asks why she included her despite considering it in her plans. She informs them that she had forgotten to tell them something very important up to this point and proceeds to tell them. While it is not revealed what she says, it is inferred she told her that their praise votes will be going to Kiyotaka instead and that Yahiko Totsuka will be expelled instead of Katsuragi. As that was the outcome of the class poll exam, Kiyotaka receiving the protection point and Yahiko being expelled.

After the exam, she meets with Kiyotaka telling him that this exam was most likely made to expel him as she had received a message from someone asking her to expel him. That most likely the exam would have have students from other classes being able to cast criticism votes on other class students making it easy to expel someone they didn't like in another class. After receiving this information Arisu had decided to protect Kiyotaka from the very beginning As they are talking about the outcome of the exam, Acting Director Tsukishiro comes up to them asking for directions and introducing himself and saying he will official start in April. As he is about to leave, he attacks Arisu can kicking her cane away causing her fall down, Tsukishiro then grabs Kiyotaka asking him to resign from school himself. He doesn't retaliate causing Tsukishiro to leave. Arisu says it was a good idea not to fight back as although he said the cameras were not recording it could have been a lie. Kiyotaka then challenges Arisu to their duel in the next exam as with Tsukishiro here their battle might be interfered with so he wanted to get it done as soon as possible.

Abilities
Along with Kōhei Katsuragi, Arisu leads class 1-A and has a group of followers that do everything she orders. Despite her limited physical ability due to heart defects, Arisu is notable for her talents as being the only person Katsuragi reports to, despite his own academic prowess and leadership skills.

She is shown to be resourceful when she was unable to go on the school cruise, as she had Masumi Kamuro conduct research on certain students and Masayoshi Hashimoto to physically manifest her plans in her stead.

Academic Abilities
Arisu is known for receiving great scores as Manabu Horikita, the current Student Council president at that time, praised her grades in the recent midterms. This was notable, as the only person he had been seen complimenting was Kiyotaka, who is extremely intelligent and skilled in manipulating his academic ability in his own right.

Intellectual Abilities
Arisu is known for her vast intelligence, which even gained praise from many people of other classes such as Honami Ichinose, the representative of class 1-B who reported to her teacher Chie Hoshinomiya that Arisu is someone to watch out for.

Name Etymology

 * The name Arisu consists of kanjis that mean "exist" (有) (ari) and "tree" (栖) (su).
 * Arisu's surname Sakayanagi consists of kanjis that mean "slope" (坂) (saka) and "willow" (柳) (yanagi).

Trivia

 * In the light novel, Arisu debuts in Volume 5; however, in the anime, she first appears in Episode 1, which chronologically takes place much sooner than the light novels.
 * Arisu ranks #21 in the "Female Character" category in the 2021 edition of 's  guidebook.
 * For the 2nd Year arc, when asked about her aspirations for the next year, she answered  'To lead a school life that's interesting... And protect my beloved person from unwanted vermin I suppose.'