Over many years, a peculiar wanderer has roamed Japan, identified only by the blade he bears—Onikirimaru. Though he appears human, he is an ogre who has pledged to eradicate his own species, yearning to one day attain full humanity. On this blood‑laden journey he observes countless human calamities and realizes that he alone blocks the ogres from annihilating humanity in the shadow of impending doom, he remains steadfast until the final battle unfolds.