A legendary Japanese swordsmith
. Along with Masamune, he is one of the most famous. His swords were of exceptional quality, but are said to be cursed
According to legend, he is said to have been possessed by a demon, and as a result, all swords he crafted have an insatiable lust for blood. This is shown in the story of the two swords in the river. Muramasa's sword sliced every dead leaf that passed by it in two, while Masamune's sword didn't touch a single leaf.
His descendants continued making swords, however like Muramasa's own, they were also said to bring about bad fortune and bloodlust, and were unpopular to own.