Sumire has been married to her husband for over twenty years. They have lived a happy life, but as a woman, she has not been satisfied for a long time. Unsatisfied with her sex life, she spends her days satisfying herself alone. One day, her son finds her masturbating. "If you make noise, Dad will wake up," his son says, pushing Sumire down. From then on, she ends up servicing her son, hiding from her husband. Then, a few days later, her son's friend comes to visit. His crotch swells when he sees Sumire's big breasts. Urged by her son, she has a threesome with her mother and her friend...