Unknown to humankind, a war is brewing between a demon named Eko and a spectral creature known as the Karas. Eko's followers are able to exist in the material world, but at a very high price - they must feed off of the fluids of humans in order to remain. They leave destruction and massacre behind them, each time leaving a solitary survivor in their wake. Nue is a demon who also lives in the human world, but refuses to kill humans. All are on a collision course in a battle that will decide the fate of humanity.