Naho's daughter is married to a man named Atsushi, and she is five months pregnant with his child. Naho lost her husband at an early age and has since been living happily with her daughter and son-in-law, forming a close-knit family of three. However, one day, when Naho steps out of the bath, she catches Atsushi secretly checking her underwear. Atsushi quickly flees in panic. From that moment on, a complex and illicit relationship begins to unfold among the mother, daughter, and husband, escalating into forbidden desires and creampie-filled encounters.