Chibo no kyôsei aibu: Tomenaide!.

A family lives in a house near Tokyo. Kiwako, the mother, who gives off a pure and innocent impression during the day, wants her husband's affections almost every night. However, her husband finishes quickly. Frustrated, she pretends to wash off her sweat and retires to the bathroom. Her son Kazumi is listening in from the other side of the door...