The Kato family, where the wife, husband, and father-in-law live happily together. However, troubled by not being blessed with children, she consulted her father-in-law. Although her father-in-law couldn't find an answer, the wife, who thought that her husband had many siblings and that her father-in-law's sperm might be strong, ends up asking her father-in-law to inseminate her. What started as a business gradually leads to her becoming addicted to sex with her father-in-law…