The story of two pairs of mothers and sons. A son, Yokozawa Tatsuo, lives alone while attending a university in the Tokyo metropolitan area. For home renovation purposes, his cousin Nakanishi Masaru and aunt Nakanishi Minako are staying at his mother's house, Yokozawa Saeko—essentially, Tatsuo's childhood home. One day, Tatsuo returns home as planned but finds himself unable to suppress his sexual arousal towards his mother, leading him to engage in intercourse multiple times and ejaculate inside her. Around the same time, Masaru is also having an illicit relationship with his own mother, Minako. Furthermore, they both witness the incestuous acts between Tatsuo and Saeko.
