The Sawamura family's father has been away on a business trip and hasn't been back home for a while. The mother, Reiko, and her son are envied by the neighbors for their close relationship, but in reality, the two have fallen into a forbidden relationship that goes beyond the roles of parent and child. It's unclear whether it started out of loneliness or a twisted love, but of course they know it's not allowed. Then, one day, the father returns from his business trip. "This is the last time..." They prepare themselves and start having sex, and a pleasure they've never felt before runs through them...