Hachimaru is a boy so frail he cannot survive without life support, and he passes his days lost in online games. His world cracks open when his robotic pet Hayataro drags home a Daruma doll; once Hachimaru draws eyes on it, the doll becomes a cat-like warrior named Daruma who claims to be a samurai. In this galaxy samurai are cyborgs bound to a key, and Hachimaru may carry one of the seven keys that open Pandora's Box, the artifact the warrior god Fudo Myo-o once used to save the universe.