Kaori Maejima is a third-year piano student at Shukusei Music Academy. As the chairman's granddaughter, she frequently leverages this status to assert influence, reflecting her strong attachment to money and power. She possesses cascades of long, wavy blonde hair styled with side tails, striking green eyes, a pale complexion, and stands 158 cm tall with measurements of 84-58-88 cm. She is often seen in her school uniform, a pleated skirt, or a nightgown.

Notoriously arrogant and haughty, Kaori exhibits a proud ojou-sama attitude and dismissively refers to the protagonist as "Katou." She harbors a distinct, unexplained dislike for teacher Minami Ayaka. Within the academy, she reigns as the prominent "queen," widely regarded as extremely beautiful.

This status and beauty make her a primary target for dormitory manager Shusaku, leading to victimization where she is drugged and ensnared in his exploitative schemes aimed at blackmailing and humiliating residents. Her background includes not being a virgin, a rivalry with fellow piano student Nagisa Kondo, and a friendship with Asami Kurihara. In response to Shusaku's actions, Kaori eventually shifts from victimhood to resistance, collaborating with Eri Takabe to actively oppose his exploitation of students; the outcomes of this resistance remain undocumented.