Ittō Kangetsu is a skilled swordsman in feudal Japan afflicted by a supernatural curse after an encounter with a malevolent spirit. This curse manifests as a demonic arm granting immense power while threatening to consume his humanity. It originates from a broader conflict between humanity and supernatural forces plaguing the world.

Driven by redemption and a need to protect others, he journeys to rid himself of this affliction. His path involves confronting vengeful spirits and demonic entities tied to specific locations or historical events across feudal Japan. These encounters unravel deeper layers about the curse’s origins and the wider supernatural conflict.

His internal struggle remains central—constantly grappling with the temptation to wield the demonic power against threats while fearing the loss of his humanity. This conflict pits harnessing the arm’s strength for protection against resisting its corrupting influence. His journey demands sacrifice and navigates moral complexity as he battles both external supernatural threats and his own inner darkness.

Key individuals shape his path: a priestess provides crucial knowledge of the supernatural world, aiding his understanding and resistance against the curse. A rival swordsman presents complex motivations, sometimes opposing him and potentially seeking to exploit the cursed power. These relationships offer contrasting perspectives on the curse’s nature and impact.

His development involves uncovering secrets about his past and the curse’s true nature through episodic battles and revelations. This progression builds toward a climactic confrontation testing his resolve to retain humanity while wielding power against significant supernatural adversaries. The narrative portrays his relentless battle to maintain his identity against the corrupting force within.