Well, in the fifteenth century, there was another swordsmith named Muramasa. For whatever reason, there were stories that his swords were possessed with malice and bloodthirst--the polar opposites of Masamune's swords, which were supposed to be pure. The main depiction of this was in the myth that if you took one of Muramasa's swords and stuck it in a riverbed, all the leaves floating downstream would be attracted to the blade and end up cut in two; meanwhile, if you stuck one of Masamune's swords in the riverbed, all the leaves would float peacefully on by.