High school students Koji and Kazuhiko are the best of friends. Koji has developed a crush on Haruyo, a music teacher who has arrived at the school as a substitute for a teacher on maternity leave. Just as he is fantasizing about having sex with her, the ghost of his late mother, Yukiko, appears. Caught in the act while peeking into Haruyo’s home, Koji manages to cover his tracks by claiming he wants to take piano lessons. From then on, Haruyo begins giving him lessons, and through a series of unexpected turns, the two end up becoming intimate—but...