After bereavement of her husband, Rieko raised her son Kosuke with just one woman. - As Kosuke grows up, she begins to have wicked feelings towards her mother from her sexual awakening. - But even though she realized that, she was spending her time pretending not to see her. - And on the eve of his marriage, Rieko finally gave her mother and child sex education, saying to Kosuke, who can only masturbate, Tonight is the last night I spend with my parents. - However, her uncontrollable desires drive the two into further forbidden acts ...