Private tutor Satsuki Kirioka is asked by her acquaintance Mr. Yamagata to tutor his younger brother. Though she'd normally decline such a request through her agency, she agrees due to their close proximity as neighbors. Upon arriving at the Yamagata residence, Satsuki waits alone in the younger brother's room and, overcome by loneliness, begins masturbating. Unaware that the older brother has quietly entered and is watching her, she continues until she suddenly realizes she's been seen, trembling with embarrassment and regret.