Driven by human greed, the great serpent named Isimi was sealed deep underground. By chance, a wandering boy named Cheonseo stumbles upon him, helping Isimi regain his reason. Cursed with misfortune, Cheonseo narrowly escapes death with Isimi’s aid, but in return, the serpent demands a price: Cheonseo’s blood to restore his strength. And for reasons unknown even to himself, Cheonseo accepts this perilous wager without hesitation…