The story of two sets of mothers and sons. Tatsuo Ishibashi lives alone while attending a university in the Tokyo metropolitan area. For home renovations, brothers Yōhei and Yasuhiro Yamaki, along with their aunt Azusa Yamaki, are staying at the house of Tatsuo's mother, Yūko Ishibashi—essentially, they are living at Tatsuo's family home. One day, Tatsuo returns home with his girlfriend as planned, but he cannot contain his sexual excitement towards his mother and, leaving his girlfriend aside, engages in sex multiple times after indulging in lewd fantasies. Around the same time, Yasuhiro also can't hold back and has sex with his own mother. Furthermore, the sons end up witnessing each other's acts of incest.
