In a not-too-distant future Japan, one Samurai-reenacting robot--a Yojimbot--makes the choice to help a human boy in danger.

While attempting to flee an entirely robot-inhabited island, Hideo and his son Hiro are attacked by a troop of armored humans. When Hideo sacrifices himself to save his son, a lone Yojimbot stands between Hiro and his death. Joined by other Yojimbots that come to his aid, Hiro and his protectors venture across the ruined island to find the mysterious "rights holder" who may hold the key to Hiro's escape. But more dangerous foes lie between Hiro and his freedom...