Arisu Sakayanagi attends Tokyo Metropolitan Advanced Nurturing High School as the representative leader of Class A. She has short lilac hair, violet eyes, and a petite frame standing 150 cm tall. A congenital heart condition limits her physical capabilities, necessitating a cane for movement and contributing to her fragile appearance compared to peers. She typically wears the standard female school uniform, frequently accessorized with a black beret and thigh-high white stockings with garter belts. Her personality presents an outwardly calm and composed demeanor combined with strategic ruthlessness. She adopts a "go with the flow" attitude, accepting situations without overt protest, but openly voices disdain for boredom. Though her soft-spoken tone can put others at ease, she enjoys manipulating people and situations for her objectives. She exhibits confidence and intellectual arrogance, especially when challenged, maintaining an aura of imperturbability in most interactions. However, she reacts strongly to comments about her stature, such as the nickname "Little Girl," viewing them as undermining her authority. This sensitivity contrasts her usual composure. She demonstrates vindictiveness when provoked, orchestrating Haruki Yamauchi's expulsion after he insulted her and caused her to fall by pretending interest to facilitate his removal. Her background centers on her relationship with her father, the school's former chairman. A childhood visit to the White Room facility, where she witnessed Kiyotaka Ayanokōji dominate other children in chess, shaped her belief that genetic superiority determines potential, not education or environment. She resolved to prove her innate superiority by defeating Ayanokōji and the White Room's philosophy, forming her core motivation. As Class A's leader, she employs strategic manipulation to maintain control. She initially shared leadership with Kōhei Katsuragi but systematically undermined his authority, eventually reducing him to a subservient role after expelling his supporter Yahiko Totsuka. Her faction includes close ally Masumi Kamuro, her right hand who monitors targets like Ayanokōji, and Masayoshi Hashimoto, who provides physical protection and executes her plans. She demonstrated tactical acumen during exams like the Paper Shuffle, directing Class A to target Class B instead of the weaker Class D to secure a 100-class-point victory. She later interfered directly in Ryūen Kakeru's interrogation of Rokusuke Kōenji, showcasing her willingness to engage in class conflicts. Her relationship with Kiyotaka Ayanokōji forms a central narrative thread. She identifies him as the White Room's "masterpiece" and declares herself the only one worthy of "burying the false genius." In their first private meeting, she revealed knowledge of his White Room background and her eight-year awareness of him, despite his lack of recollection. She tasked Kamuro with observing him and expressed explicit interest in his growth and motivations, stating she "wants him" and does not mind becoming his enemy. She acknowledged his intellectual superiority in broader strategic contexts but believes she can defeat him in structured contests like chess. These interactions reveal a layer of vulnerability not shown to others. She maintains complex rivalries with other class leaders. She acknowledged Ryūen Kakeru's ambition to rule the school with amusement but later provoked him by using Kōenji's nickname for him ("Dragon Boy"), leading to a physical confrontation where Hashimoto intervened. She considers both Ryūen and Honami Ichinose capable of providing limited entertainment, though neither matches Ayanokōji's level as a challenge. After Katsuragi defected to Ryūen's class, she treated his betrayal as expected and welcomed the increased challenge. Her capabilities are reflected in her Overall Ability Assessment scores: Academic Ability: A (93), Adaptability: B+ (80), Physical Ability: D- (25), Social Contribution: B- (65), resulting in a B (66) overall. Chess proficiency is noted as her specialty, while her hobby is observing Kiyotaka Ayanokōji. She dislikes "dirty things." Despite physical limitations, she commands respect through intellectual dominance and strategic manipulation, establishing herself as a benchmark for other class leaders.