After losing her husband, Yuria raised her son on her own with unwavering dedication. Her son was about to graduate from university. However, there was something that troubled her—years ago, she had once crossed the line and become physically intimate with her son. That incident became the catalyst for a hot spring trip together, meant to be a final memory before his graduation. As they travel, memories of that day resurface. Soaking together in the hot springs, alone together in their private room, the boundaries of their mother-son relationship begin to blur. What little restraint they had soon vanishes, giving way to raw instinct, as the two are drawn into a forbidden relationship. A story of incestuous desire unfolds here.