Keiko was a high school teacher in a provincial city, but due to a certain incident, she quit school and moved to Tokyo, where she now teaches English at a prep school. The incident was a tragic incident in which she tried to save a student from being gang-raped by a thug, only to end up being tied up and tortured instead. Since then, she has become a perverted sex-obsessed person who gets pleasure from the pain of being tied up. The man who transformed her like this follows her around like a tick, and although she hates him, she cannot leave him...