Kanzaki Aoi and Kurusu Akito have ended their childhood bond and are no longer a couple. Kaya, a girl who has had feelings for Akito, decides to take Aoi's place. However, her attempts to make him forget Aoi fail, as Aoi chose their P.E. teacher, Shudo, driven by lust and has become his mistress. While trying to win Akito's affection, Kaya is blackmailed into performing sexual acts with a man who has been watching her. As she is forced to submit to his demands, Kaya starts having obscene thoughts about Shudo. Little does she realize that the teacher has been orchestrating this entire situation...