Kazusa Ootori is a 16-year-old student at Himesaka Girls' Academy, renowned for her exceptional skill in playing the koto. Her family carries a deep legacy with the traditional Japanese instrument, including her skilled mother. Kazusa began playing in early childhood, yet developed significant stage fright after a traumatic performance event. This fear initially prevented public performance, though she gradually overcame it through experiences with her musical peers. She possesses light, long wavy hair and brown eyes, typically seen in her Himesaka Girls' Academy uniform. Kazusa often projects a fierce aura, which reportedly deterred romantic interest from boys. Beneath this exterior, her personality reveals complexity: initially appearing aloof and distant, she shows vulnerability, kindness, and a capacity for meaningful friendships. She enjoys confections with cute appearances and dislikes grotesque things. During holidays, she listens to performances by fellow koto player Satowa Hozuki, practices koto, or goes shopping with her friend Fumi Hanamura. Kazusa forms a significant, multifaceted connection with Satowa Hozuki, whom she deeply admires for her musical talent. This admiration borders on obsession, driving Kazusa to actively pursue Satowa to join her school and play koto together. She openly expresses the view that members of Tokise High School's koto club are unworthy of Satowa's skill level, reflecting her strong stance on musical excellence. Concurrently, Kazusa maintains a close friendship with Fumi Hanamura, frequently spending leisure time shopping with her. Her relationship with her father appears strained, impacting her musical expression and personal growth. Her character development centers on confronting personal challenges like performance anxiety and interpersonal relationships. Through sustained involvement with koto club members, she cultivates greater confidence and forms deeper emotional connections. This journey highlights her evolution from an isolated perfectionist towards collaborative musicianship and mutual support. Her surname "Ootori" (凰) translates to "phoenix" or "female phoenix bird," symbolically reflecting her transformative journey.