Mai Fuyuki, 44 years old. With her husband absorbed in work, she found herself drawn to the gentle and warm presence of her son. Before long, her feelings for him shifted from maternal affection to seeing him as a man. These emotions grew into overwhelming, taboo desires. Today, they're alone together on a hot spring trip. Staying at a mixed-gender onsen inn, she struggles to suppress her feelings, terrified that her body will betray her and crave his touch. How can she possibly overcome these forbidden emotions?