One year ago, Reiko, a beautiful and kind mother, came to Japan after remarrying. Her new family consists of her husband and her college student son-in-law, Tomoma. Reiko is masturbating in her Japanese-style room. Her son, Tomoma, is walking down the hallway and happens to see the scene. At dinner, Tomoma tells him that he watched his mother masturbate without meaning to, and he gets angry because he can't do anything because he is worried about Reiko. After having sex with her husband, Reiko is worried about her son and goes into Tomoma's room. Her son, Tomoma, suddenly hugs her and asks for her hand. Reiko is confused, but she accepts to have sex with her son...