A child born of a dead mother is abandoned by his father and is seen as unlucky by the villagers because he was born with Bulgasal’s curse. The little kid gets adopted by the general of Goryeo and names him Hwal. He grows up to become a warrior who kills monsters. He has killed all the monsters except Bulgasal, who they still don’t know if he is a myth or real. The creature is indeed real, and she finally shows up and kills all of Hwal’s family-his father, wife, and son. As if that wasn’t enough, the monster turns Hwal into a Bulgasal instead of killing him. The Bulgasal becomes a human by stealing Hwal’s soul.
Since that day, Hwal has been searching for the Bulgasal for 600 years to get his soul back, but every time she is killed by other monsters who have reincarnated as humans. After his relentless search, Hwal finds Bulgasal born as twins, but one of them, Sang Yeon, is killed by a monster, and the other one, Sang Un, runs away with her younger sister, Si Ho. After some years, Hwal finds her again, and a series of unprecedented events start happening in both Hwal and Sang Un’s lives. All these years, Hwal believed that he was the only Bulgasal in existence and Sang Un believed he killed her family, but another Bulgasal appears and changes the flow of their lives completely.
As the mystery unfolds, everyone from Hwal’s past life starts appearing. All of them are connected through Karma, and they have come full circle now. Alliances are formed and broken every time a new mystery is unveiled. A battle among three antiheroes and their karmic connections is bound to bring misery to all of their lives as they pay for their deeds.