Kyoko, a neglected stepmother married to a man who ignores her sexually, lives with her husband and his son, Yoshio. Sensing her loneliness, Yoshio begins to seduce her, gradually turning her into his sex slave. While her husband is away, she endures increasingly lewd treatment from her stepson. During her husband's business trips, Yoshio invites his friends over, dragging Kyoko deeper into a world of depravity. Each encounter brings her new, overwhelming pleasures she cannot resist.