Toshiki is addicted to gambling, hiding it from his wife. Today, he won big at the motorboat races, which is rare for him, so he goes to a super high-class soapland to reward himself...and to his surprise, it's his wife's mother who shows up! "What are you doing, mother-in-law?!" "Toshiki?! Please don't tell anyone!" Toshiki is left speechless by the true identity of his mother-in-law, which he never imagined. "You know... if you keep it a secret... I'll give you plenty of service." He is seduced by the slender body that he has been interested in for a long time, and when he gives himself over to her... her superb sexual techniques bring him to the climax!