During her husband's prolonged business trip, Sawako lives day to day with her stepson Shouta. One day, Shouta invites a friend over and, arriving earlier than expected, waits inside Shouta's room. Meanwhile, Sawako notices faint moaning sounds and peeks into the room, catching the friend masturbating. Though shocked and flustered, the boy can't hide his surprise—yet Sawako calmly begins stroking his crotch. This sudden turn of events pushes both into an unexpected new relationship.