Goro, the father-in-law who comes to Tokyo to visit his son's couple, sees how busy his son is and realizes that the couple has no sex life. Because he is waiting for the birth of his grandson, he is convinced that improving his daughter-in-law's sexual appeal is essential. One night, Goro, having made up his mind, forcibly has a relationship with his daughter-in-law. He trains his daughter-in-law, who was shy about sex, day after day, leading her to become a prisoner of carnal desire, but an astonishing ending awaited him that only her son didn't know about…