The Shinmura family lives happily with their wife, husband, and father-in-law. However, she was troubled by the difficulty of having children and consulted her father-in-law. Her father-in-law also couldn't find an answer for her, but she thought that her husband had many brothers and her father-in-law's sperm was stronger, so her daughter-in-law asked her father-in-law to inseminate her. I end up asking for it. At first, she thought it was just her business, but she gradually became addicted to sex with her father-in-law... for the first time.