Miki, a housewife living with her husband and son. Perhaps because she turned forty and her libido increased, she spends her days with few nighttime encounters with her husband and accumulating frustration. In order to attract her husband's attention, she masturbates as a method to increase pheromones written in a book. Her son, who came home, happens to see it. The son escapes to the second floor so as not to be noticed. That night, Miki's back hurts, so she asks her son for a massage. Next, Miki massages her son. She notices her grown-up son's dick and stares at it without thinking…