Yumi, a mother living with her husband and son Seiya, had a secret. She loved her only son Seiya so much that she would satisfy his sexual needs behind her husband's back, hoping to get rid of his worldly desires. However, her lewd actions, which she thought were for the mother's own good, eventually fueled her son's hidden desires. Seiya began to desire sex with his mother, and he could no longer suppress that desire. Reflecting on her own actions, Yumi realized that she could not resist Seiya's demands and finally crossed the forbidden line...