Binh, the elder sister, finds Phuoc masturbating in their shared bathroom. Instead of shaming him, she joins him, their secret becoming a shared addiction. They explore each other's bodies, Binh teaching Phuoc the art of pleasuring a woman. Their sessions grow bolder, ending only when their mother threatens to return home. One day, Phuoc finds Binh waiting in their room, naked and ready. He takes her missionary, then pounds her from behind, Binh's moans echoing through the house. They climax together, their bodies entwined, before hurriedly cleaning up, their secret safe, for now.