In a time of dire need, humanity turns to a demon when the gods remain silent. The demon, wielding the bloodthirsty sword Zsoltgewinn, indiscriminately slays its summoners. Sealed away for ages, the sword resurfaces in the hands of the Shoshidai, a group that collects cursed relics. Yet, the sword's corrupting influence drives the administrator, Takuma Miura, to abscond with it. Meanwhile, Gai Ogata's family suffers a tragic fate due to another demonic blade, Shiryu, leading to his upbringing by Amon, a skilled blacksmith. Gai, fixated on Shiryu, hones his craft until a mishap grants him a new arm—forged from Shiryu. Now burdened with a cursed limb, Gai grapples with its violent nature as Zsoltgewinn leaves a trail of destruction in its wake.