Gozo, a father-in-law who comes to Tokyo to visit his son and his wife, notices how busy his son is and realizes that the couple is not having sex. As he is eagerly awaiting the birth of their grandchild, he is convinced that it is essential to improve his wife's sexual appeal. One night, Gozo makes up his mind and forcibly has sex with his wife. He trains his wife, who is sexually shy, day after day, and soon leads her to become a slave to carnal desires, but a shocking conclusion awaits him that only his son does not know about...