Nami drops out of college and invites her son, who stays at home, on a hot spring trip to get him out of the house. The two have previously become lovers, and despite being step-parent and child, they struggle with conflicting emotions between familial bonds and romantic feelings. During the trip, her son suddenly confesses his love. Though she knows it's wrong—seeing traces of her late husband in him—they can't resist each other any longer. She takes his hardened cock into her mouth, surrenders to his embrace, and drowns in pleasure, repeatedly copulating with him. This is a story of forbidden mother-son incest.