Valentine's Day brings an unexpected twist for young sisters Nam and Nim. While exchanging gifts, their hands linger, and they find themselves drawn to each other's warmth. Nim's breath catches as Nam's fingers brush against her thigh, sparking an intense, forbidden desire. They tentatively explore each other's bodies, their virginity making this Valentine's Day a unique and intense first experience. As they climax together, they realize they've shared a secret they'll carry close to their hearts, forever intertwined.