When the toilet at the Terasaki household suddenly breaks down, mother Izumi is stuck attending to the repairman and suddenly feels an urgent need to pee, reaching the brink of incontinence. With no other option, Izumi is forced to urinate shamefully in the backyard, only to be caught in the act by her son Keisuke, who had been asleep. Overcome with arousal at the sight of his mother's humiliating act, Keisuke can't restrain himself and attacks her while she naps.