), a brilliant scholar who loses his family and friend 120 years prior due to the machinations of the evil vampire, Lee Soo-hyuk

). Sung-yeol is transformed into a "guardian vampire" and spends his immortality seeking a secret plan to destroy Gwi. The modern timeline begins when Sung-yeol meets Jo Yang-sun

As the days turned into weeks, their lives became entwined. Yang-sun became his eyes during the daylight hours, and Sung-yeol became her protector in the dark. But the memorandum revealed a grim truth: to kill Gwi, a sacrifice of human blood was required—blood from the lineage of the one who first invited the demon in.

Often called the "King of Sageuks," Lee Joon-gi delivers a masterclass in physical acting. He balances the predatory grace of a vampire with the crushing grief of a man who has lost everyone he loved. His ability to convey pain through his eyes remains the show's strongest asset.