Shiki/corpse demon

this is manga-based anime, were when a human/animal is dead for a long time they become a Shiki. a demon powered by the humans horrible, terrible, desperate feelings. hiki/corpse... need living blood to survive so they are forced to feed on human flesh with bloodshed and battles...a doctor had experimented and decided to fight for humanity the experiments were cruel, and ruthless merciless. User: has to make a choice to join the Shiki's side as a human or the human's side.