The Kato family lives together with three people: daughter-in-law, husband, and father-in-law. However, she was troubled by the fact that she was not blessed with children, so she consulted with her father-in-law. The father-in-law could not find an answer, but the daughter-in-law, who thought that her husband had many brothers and her father-in-law's sperm was strong, asked her father-in-law to seed her. At first, I thought I started it as a business, but gradually I got into sex with my father-in-law ...