So have we determined here that Garai has turned the Masamune evil?
I would think, considering the way Dario fights, and considering his black elemental type, that something far greater than Garai's hopes and dreams corrupted the Masamune. I mean we're talking about one of the most powerful artifacts in both major games here. I'm thinking there had to be some outside influence in the corruption of the Masamune. It is even possible that when Frog died, the sword was sealed away for many years, allowing Masa and Mune to fall asleep. They could have been restraining the evil created in the sword when it was forged within the Mammon Machine, and when they fell asleep, it manifested itself as another controlling entity for the sword. Thus the different shape, color, and capabilities it has.