Kazusa Ōtori is a supporting character in the second season of the anime, serving as a student from Himesaka Girls' Academy, a rival school to the protagonists at Tokise High School. She has a fair appearance with long, light, wavy brown hair and brown eyes, and is typically seen in her school uniform. Her birthday is on June 7, and her zodiac sign is Gemini. She stands at a height of 155 centimeters.

Regarding her personality, Kazusa is known to give off a fierce or intense aura. This demeanor has contributed to a lack of romantic interest from boys her age. Despite this, she has a notable appreciation for cute things, particularly confections that look aesthetically pleasing, and she dislikes grotesque subject matter.

Kazusa's primary motivation within the story is deeply tied to her admiration for Satowa Hozuki, the gifted koto player who eventually joins the Tokise High School Koto Club. She holds Satowa's playing in very high regard and is persistent in her attempts to recruit Satowa to attend Himesaka Girls' Academy. Her desire is to perform the koto alongside Satowa, as she believes that the members of the Tokise club are not worthy of her idol's talent. This intense interest sometimes borders on a slight obsession with Satowa.

Her most significant relationship is with Satowa Hozuki, whom she greatly admires and pursues. In contrast, her relationship with the Tokise High School Koto Club is one of underestimation, as she initially dismisses their abilities as inferior. On a more personal and friendly level, she has a close bond with her friend and classmate Fumi Hanamura. The two are frequently seen together, spending their free time shopping and socializing.

During school holidays, Kazusa's typical activities include listening to recordings of Satowa Hozuki's performances and practicing the koto, which suggests a dedicated approach to her musical craft. She also enjoys going shopping with her friend Fumi Hanamura.