During humanity's most desperate hour, with no divine aid arriving, they called upon a demon for help, who brought the sword Zsoltgewinn. But this blade, driven by an endless craving for blood, turned against its summoners, leading to its eventual confinement. Centuries later, the Shoshidai, an organization dedicated to collecting cursed artifacts, uncovered Zsoltgewinn. Its overwhelming power proved impossible for humans to control, corrupting administrator Takuma Miura, who then escaped with the sword.
Meanwhile, Gai Ogata's existence is forever altered by another cursed blade, Shiryu. His father is killed, and his mother takes her own life shortly after Gai's birth. Left in the forest with the sword in his grasp, Gai is found by blacksmith Amon. Over time, Gai becomes deeply fixated on the sword and grows into a master craftsman. After losing his arm in an accident, he receives a new one, which is actually the reforged Shiryu.
Now wielding a cursed sword as his arm, Gai must learn to tame its savage nature. At the same time, Zsoltgewinn continues its violent path, spreading destruction wherever it goes.