Son Taichi found himself increasingly aware of his mother, Wako, as a woman, day after day. Then came an event that deeply stirred his emotions. One day, Wako suddenly said, "If it's just once, and not at home, it's okay." Confused yet overwhelmed, Taichi felt a long-suppressed desire rise within him. Seizing her words as a chance, they embarked on a one-night, two-day hot spring trip together. The intimate time shared between mother and son, and the turbulent emotions that unfold, form the heart of this story.