In medieval Japan, a young samurai is dishonored at the hands of the demon Agat for killing his master and letting him live. Now, after years of training with a magic/cursed sword, the now masterless Ronin seeks the demon out for vengeance and the hopeful joining of his master in death. The plot only thickens, however, when he and the demon are trapped in the sword and finally released in the New York City of the bleak future to do battle once more.