The Kobayashi family of three, consisting of a wife, husband, and father-in-law, live harmoniously. However, they are troubled by their inability to have children. Since the husband has many brothers, the wife suspects that her father-in-law's sperm might be too strong, so she asks him for insemination. What started as a business-like arrangement gradually turns into an obsession with sex with her father-in-law. When she finds out she is pregnant, their relationship ends. But after giving birth, they can no longer hold back and resume insemination and mating…
