With the third anniversary of her husband's death over, Chisato has decided to live with her son and his wife. At first, there was tension between her and her son's wife, but they seem to have built a good relationship and are living happily together. However, Chisato's body aches due to the loneliness of her husband's absence, and she distracts herself by masturbating, which has become a daily routine. Late at night, she was soothing her aching body again today, but her son saw her doing so. Just as she was reaching orgasm from the act of soothing herself, her son appeared and inserted his hot erect rod into Chisato's body, despite her refusal. Although it was forced, Chisato gave in to his desire, and after that she did as her son asked, but gradually Chisato began to desire her son. At that time, something strange happened to Chisato's body. Her period ended. Feeling that her life as a woman was over, Chisato told her son about it and asked to end their relationship, but...