Kaho and her son Hiroshi share a close mother-son bond. They had always made it a yearly tradition to go on a hot spring trip together as a family, but this year, her husband became too busy, leaving just the two of them to travel together. The absence of her husband brings to light the subtle tension between them, stirring emotions they had long kept hidden. Kaho is unhappy in her marriage, and it becomes clear that Hiroshi has begun seeing her as a woman. Initially resisting due to social taboos and fear of judgment, Kaho gradually gives in to overwhelming desire. The story unfolds as they grapple with their maternal bond and newfound passion, ultimately giving in to their forbidden attraction.