Maiko Morisawa is the school nurse at Ikaruga High School, where Kasumi Miyatsuji serves as chairperson. Her position brings her into close contact with students, including Kaneshiro Shoichi, who develops an intense physical obsession with her. She exploits Shoichi's fixation, leveraging his fear of expulsion if he fails an upcoming exam. At her urging, Shoichi steals an examination disk containing test answers from the principal's office. Kotono Miyatsuji discovers this theft. To prevent her from exposing him, Shoichi assaults Kotono.

Maiko's manipulation continues beyond this event. When Suzuyo Miyatsuji, Kotono's younger sister, uncovers the affair between Maiko and Shoichi, Maiko orchestrates a violent gang rape against Suzuyo to silence her. This action forms part of Maiko's broader scheme to ensnare the Miyatsuji sisters in escalating exploitation. Her plan ultimately targets the entire family, including their mother Kasumi. As the scheme progresses, Kasumi falls prey to Shoichi's advances within the environment of depravity Maiko cultivated.