Kasumi Amamiya, a college student preparing for academic examinations, resides at Kazahana Inn alongside fellow student Seiichi Itoh. Recurring evening noise disturbances within the boarding house disrupt her studies, fracturing her concentration and hindering her coursework focus.

She maintains a persistent fixation regarding her own posterior, frequently making verbal slips that inadvertently expose this preoccupation despite attempts to conceal private activities in her room. This behavior often coincides with her possession of a cucumber — explicitly not for consumption — during confrontations about disruptive noise. Such encounters typically involve her abruptly entering rooms while visibly agitated and clutching the object.