The Kitetsu sword in the One Piece series is known to be a cursed blade. The curse associated with Kitetsu is a fictional element introduced within the story.

The exact details of the curse are not explicitly explained in the series, but it is believed that the curse brings misfortune or tragedy to those who wield it. The curse is likely a literary device used to add intrigue and danger to the sword's lore.

It is worth noting that Kitetsu is not a single sword but a series of blades crafted by different generations of swordsmiths from the Kitetsu family. The specific sword referred to as Sandai Kitetsu is the third generation sword in the Kitetsu line.

The curse surrounding the Kitetsu swords is meant to create an aura of mystery and danger, enhancing the significance and reputation of these blades in the world of One Piece.