An won a hot springs trip through a lottery at the shopping district and, without telling her husband, set off on a journey with her son Yosuke. Contemplating divorce after being betrayed by her husband, she hoped to find emotional clarity by spending time with her son. But when she reveals the truth, her son is visibly shocked—and in that moment, he begins to recognize the romantic feelings he's secretly harbored for his mother since childhood. His growing awareness of her as a woman awakens a deep desire for her body. Meanwhile, An, seeking comfort from her emotional pain, finds herself drawn to her son's physical presence. The shifting emotions between them deepen the intimacy of this forbidden journey.