Her son had gradually begun to view his mother's big tits in a sexual way, and realizing this made her emotionally distant toward herself. Fearing that this situation would bring unhappiness to both of them, she resolved to create distance between them. However, Eri, the mother, feeling loneliness from her son's cold behavior, was deeply saddened by this decision, and decided to invite him on a hot spring trip—one final farewell. In the private space of their getaway, with her voluptuous breasts on full display before him, mother and son cross the line into forbidden intimacy. Falling into the sweet trap of incest, they copulate repeatedly, their fate drawing deeper with each act. As their bond and raw desire intertwine, the forbidden romance unfolds—how will it end, and what conclusion awaits them at the journey's close?