After twenty years of marriage and raising her son Keita to adulthood, Sayuri Ikui felt fulfilled, having completed her duties as a mother, and lived each day in peace. However, her tranquil life came to an abrupt end due to a sudden incident. One day, Sayuri was raped by Kobayashi, a young man who delivered newspapers, without any clear reason. The traumatic event left deep psychological scars, and gradually, the physical sensations imprinted by Kobayashi's cock began transforming her from a "mother" into a "woman."