What makes a Zoro sword a "demon sword" in One Piece?
Updated Mar 2026
In One Piece lore, a demon sword - or "cursed blade" - is a katana said to have a will of its own, bringing misfortune or even harm to those who lack the strength to control it. The Sandai Kitetsu is the most prominent example: it belongs to a lineage of three cursed Kitetsu blades, each ranked differently in quality. Shusui, while not cursed in the same sense, is classified as a Black Blade - a rare category achieved when a swordsman's Haki permanently darkens the steel through mastery. Enma is notable for draining its wielder's Haki involuntarily, making it extraordinarily dangerous to handle. Oda drew these concepts from real Japanese folklore around muramasa blades, which were historically rumored to inspire aggression in their owners. Replica collectors value these swords precisely because each one carries a distinct fictional biography that gives the display piece a layer of narrative meaning beyond aesthetics.