Arisu Sakayanagi is a student at Tokyo Metropolitan Advanced Nurturing High School, where she is enrolled in Class A and serves as one of its primary leaders. She is a petite young girl with short lilac hair and violet eyes, standing only 150 centimeters tall. Due to a congenital heart condition, she has a very poor physical constitution, which prevents her from participating in most athletic activities and forces her to use a cane for mobility. Her refined school uniform, often accented by a black beret, underscores an aura of calculated elegance. Arisu is a genuine genius, possessing extraordinary academic ability, strategic thinking, and deductive reasoning skills. Her official evaluation at the start of her second year gives her an Academic Ability score of 93, placing her at the pinnacle of her grade. She is a highly competent chess player, capable of competing at a national level, and her strategic outlook on class conflicts often mirrors that of a chess match, where people are the pieces to be moved. Outwardly, Arisu presents a calm, composed, and almost whimsical demeanor, rarely showing overt distress. Beneath this placid surface lies a deeply combative, cunning, and manipulative nature. She is self-indulgent and fundamentally self-centered, driven more by her personal desires than by any sense of loyalty to her class. She is easily provoked by comments regarding her small stature and holds grudges, meticulously plotting revenge against those who slight her. Arisu holds a core belief that a person’s potential is determined by innate genetic superiority rather than by environment or training. Years before the story begins, she visited the White Room with her father, the school’s chairman, and witnessed a young Kiyotaka Ayanokōji effortlessly defeating opponents at chess. Seeing this “masterpiece” of an artificial educational environment challenged her worldview, and she resolved to defeat him to prove her natural superiority. Her feelings toward Ayanokōji are complex, described as a mixture of rivalry, affection, and obsession. As the leader of the radical faction within Class A, Arisu initially shared power with Kōhei Katsuragi but systematically undermined his authority and eventually became the sole, unchallenged leader of the class. She commands loyal followers, including Masumi Kamuro, whom she tasks with observation and information gathering, and Masayoshi Hashimoto, who acts as her protector. She rules with ruthless precision, expelling dissenters and using blackmail to bind allies. Throughout the first year, Arisu operates as a major antagonist, maintaining rivalries with other class leaders such as Kakeru Ryūen and Honami Ichinose. Her dynamic with Ayanokōji intertwines rivalry with obsession, and she frames their clash as a duel between natural genius and manufactured skill. Her arc closes with a dignified defeat, accepting loss to Ayanokōji in a final rematch.