A parallel world resembling Japan's Taisho era, where the technology of the period has been joined by something darker: Crimson Katanas, weapons of enormous destructive power that must be fueled by human sacrifice. The empire has been using them to crush neighboring countries. Some of the warriors who wield these weapons have started questioning what they are doing. A small band of them has broken away and is now fighting back against the empire that created them — using the same katanas and the fighter planes that serve as the conflict's most visible technology, but turning them in the other direction.