The Mercenary, an unnamed white tiger Beastfallen, finds himself constantly on the run from bounty hunters and witches. He stumbles across a hungry little girl, who traps his latest attacker in a mud prison and reveals herself as a witch. Despite his initial suspicions of her, the Mercenary decides to share his soup and join her quest as her bodyguard to find a grimoire from a mage named Thirteen. The witch, later recognized as Zero, draws up a blood contact as a promise to return the Mercenary as a human after her quest is complete...