Takagi and Yui have been married for four years. A year ago, Takagi's parents divorced, so he welcomed his father to live with them. His father is a long-haul truck driver, often on break, so he spends a lot of time with Yui. He often says vulgar things and touches Yui inappropriately. Although Yui has told Takagi about it, he thought his father was just joking around, so he didn't pay much attention. One day, when coming home from work, Yui seriously told Takagi that his father had touched her inappropriately and sexually harassed her. At first, Takagi was very angry and decided to move out. But his curiosity and excitement about his wife having an affair with someone else made him uncomfortable. He discovered that he is someone who enjoys cuckoldry. He told Yui about it, and finally, Yui accepted the situation. He asked her to seduce and have sex with his father again for him to witness. Despite hesitating, Yui agreed because she wanted to please him. So they both returned home, had dinner, and played cards. At that moment, Takagi would pretend to be sleepy to secretly observe his wife and father having sex together...