Misuzu, a devoted wife who wished for her family's happiness, lived peacefully with her husband—until their son, Jin, returned home after divorcing due to sexual dissatisfaction. One day, while cleaning his room, Misuzu accidentally discovers her own underwear hidden there. Stunned, she stands frozen, but out of compassion for her son's wounded heart, she resolves to cross the boundary between mother and child to heal him. As a result, a hidden desire begins to grow between mother and son, giving rise to a secret romantic relationship. Beneath the surface of their once-peaceful household, a strange and intimate bond forms between them.