At long last, Kayoko Akizuki, mother of Airi and Marina, has returned home to her husband, Kouzou. Realizing her daughters have spent too long with only one parent, she is determined to mend family relations. However, little does she know that Kouzou has been having a sexual affair with his two stepdaughters for quite some time. As time passes, Kayoko grows increasingly inquisitive and seems to be finally becoming aware of the situation. Kouzou becomes desperate and aggressive in his courting, taking his stepdaughters in their sleep or in public spaces. Moreover, a new challenger for his attention arrives—further jeopardizing Airi's relationship with her stepfather.