A young wife, Yuuri, who has gotten into the habit of masturbating due to her husband's frequent business trips, is being watched obsessively by her father-in-law, who is fascinated by her large buttocks. One day, he accidentally sees her masturbating, and his suppressed sexual desire explodes. He seduces his son's wife, and this act is witnessed by the husband's colleague, leading to a chain of adulterous affairs. The adulterous wife takes another man's penis into her mouth in the couple's bedroom.
