In the bustling city of Seoul, Seunghyub, a high school senior, leads a typical life filled with exams, friends, and dreams of college. Everything changes one fateful night when he encounters Eunsol, a mysterious and beautiful girl with an otherworldly aura. Eunsol is a centuries-old vampire who has lived in the shadows, hiding her true nature while navigating the modern world. Despite their differences, Seunghyub and Eunsol are drawn to each other, forming an unlikely bond. As their relationship deepens, Jihoon learns about Eunsol's past and the dangers that come with loving a vampire. Eunsol, in turn, grapples with her fear of losing Jihoon to the inevitable passage of time and the threat of vampire hunters. Their love is tested by the clash of their worlds, the secrets they must keep, and the sacrifices they must make. Will Seunghyub and Eunsol overcome the odds and find a way to be together, or will their love be doomed to remain a fleeting moment in the long span of eternity?