Boxer Ren, to save his sister's life, signs up for a life-or-death fight. Scarlett, the reigning queen of the underground boxing arena, sees his unyielding grit, bets his slave contract to pay his medical bills, and keeps him at her side with an electric shock collar. The two share a common enemy, Leo. Scarlett treats Ren's wounds and trains him to regain his strength as they lie low together. Day after day, the icy queen and the caged beast grow a bond, vowing to defeat the rival fighter in the ring and take revenge on the underworld force Leo together—a tug-of-war romance of control and redemption in a dark city.
