During the Joseon dynasty, the nobleman Kim Sung Ryeol, who appears to be a scholar, is in fact a vampire, having become one to keep a promise he made to his friends. When Sung Ryeol was human, he discovered the existence of the vampire Gwi, who, wielding power above even the king, effectively determined the line of succession to the throne; thus, to fight against Gwi, he had himself transformed into a vampire. Will he manage to defeat the evil Gwi without losing his humanity?