After being transferred to an all-girls school, Umehara-sensei, a high school teacher who had taught at an all-boys school, reconnects with one of his former students, Hataoka Kei, who is now a college student. Despite feeling uneasy about their regular drinking sessions since Kei was once his student, Umehara-sensei continues to meet with her. However, unbeknownst to him, Kei has developed an unhealthy obsession towards him which has resulted in her exhibiting stalker tendencies.