Yuki, the new stepmother to a man's teenage sons, dedicates herself to household chores every day in an effort to earn their acceptance as a mother figure. However, when her uncontrollable desires lead her to masturbate in the bathroom, she is caught by the eldest son. This incident triggers forbidden lust within the household. Trapped between desire and morality within the family structure, Yuki becomes entangled in a new, illicit relationship.