Mother's anus stolen by son

Ayano, a mother who was abandoned by her parents and raised in an institution, dreams of a happy life as a family of three due to her circumstances, but she is heartbroken by the conflict between her practical husband, Keiji, and her son, Takayuki, who is betting on his dreams. Before getting married, Ayano was taught the pleasures of anal by her lover, who grew up in the same facility and loved her like an older brother. Since then, she has been unable to forget the taste and has always had anal sex with her husband. Takayuki, who knew about the abnormal couple's activities, had feelings for Ayano that were even greater than those of his mother, and finally crossed the line...