Taro accidentally witnesses his mother, Mirai, masturbating in the middle of the night, six years after her divorce. Realizing that his always-smiling, hardworking mother is actually a woman struggling with sexual frustration, Taro wants to help her. He confides in his friend Shota, a smooth talker and womanizer, and pleads with him, "Just once, please sleep with my mother." Surprisingly, Shota readily agrees, and they meet for dinner at Taro's house...