Yu and Sumire are full-time housewives living in the same apartment building, often visiting each other's rooms as close friends. One day, a salesman with dubious investment schemes visits Sumire's room. Yu and her husband go to Sumire's room and chase the salesman away. Although Yu and her husband save Sumire, this becomes the trigger for a gruesome incident… The salesman is actually a yakuza member who plots a cycle of revenge involving two couples. Soon after, they are forced to swap husbands and perform internal ejaculation.
