The story of two pairs of mothers and their sons. Tatsuo Asamiya, a son who lives alone while attending a university in the Tokyo metropolitan area. For home renovations, his cousins Yōhei Tanihara and Yasuhiro Tanihara, along with their aunt Yukihana Tanihara, are staying at the home of his mother, Ryoko Asamiya. In other words, they are living at Tatsuo's family home. One day, Tatsuo, as planned, returns home with his girlfriend but cannot suppress his sexual excitement towards his mother, ultimately engaging in sex multiple times after lewd fantasies. At the same time, Yasuhiro witnesses his own mother Yukihana and Yōhei having sex, becoming jealous of their enviable relationship.
