When Jo Yang Sun is driven out of house and home after her father is framed for a crime, she is forced to crossdress in order to make ends meet as a bookseller, where she meets Kim Sung Yeol, a handsome, but mysterious scholar who is actually a vampire. Meanwhile, an evil presence at the royal palace stops at nothing to keep the Crown Prince from claiming his rightful throne.
In Joseon Dynasty, immaculately dressed in scholarly robes, the young nobleman Kim Sung Yeol lives as a vampire to keep his promise to his friends. When Sung Yeol still was a human, he found out about the vampire Gwi who sits above the King deciding the next royal line and has resurrected as a vampire trying to fight against Gwi. And now, he is living as a guardian vampire fighting against the evil vampire without losing his human nature.