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 Kōhei 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 Kakeru 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 Kōhei, about their competition with B-Class, she then mentions how she initially thought Kakeru 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. Honami, 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 Honami'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. Honami 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 Kakeru'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 Kakeru 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.

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.'