Based on the game by Lilim Darkness.

Kanzaki Aoi and Kurusu Akito have broken their relationship and are no longer together. Kaya, a girl who has been interested in Akito, decides to make a move on him. However, her efforts to make him forget about Aoi fail. In the mean time, Aoi has entered into a sexual relationship with their P.E. teacher, Shudo.

During her attempts to gain Akito's affection, Kaya is blackmailed into having sexual acts with a guy who has been watching her. As she is forced to let him have his way with her, Kaya begins having obscene thoughts about Shudo. Little does she know that the teacher has been planning this all along...