Ayano Kato (34) lives with her husband, Kenichi, and they have no children. Both work full-time jobs and commute daily from the suburbs into central Tokyo. After a certain incident, Kenichi develops erectile dysfunction, leaving the couple in a sexless marriage. One day, while riding a packed train, Yoko experiences her first-ever molestation. Though shocked by the unexpected event, she gradually begins to feel pleasure in being dominated.