In the Kato household, the daughter-in-law, her husband, and her father-in-law live together happily. However, they are troubled by their inability to conceive a child. When the daughter-in-law consults her father-in-law, he is initially unable to offer a solution. Noticing that her husband has many siblings, she begins to suspect that her father-in-law has strong sperm, and eventually asks him to impregnate her. At first, their encounters feel like a mere duty, but gradually, she becomes drawn to the physical relationship with her father-in-law, entangling both their hearts and bodies. A mysterious love drama unfolds, woven from family warmth and a new, forbidden bond.