His home appears ordinary: a domineering father named Koji and a quiet, gentle mother named Yuka. The father often shouts at her, and although the son worries, she seems to accept it. One room in the house is strictly forbidden. After midnight one night, he takes a break from studying for entrance exams and notices light and moans coming from inside. Peeking in, he discovers that the voice belongs to his father—the same man who spanked his wife during the day is now delighted to be spanked by her as she wears obscene lingerie. From then on, the adult son role-player learns firsthand that his mother is the true ruler of the house...