Every thousand years, mamodo descend upon earth to conduct the ultimate battle. The winning mamodo becomes the king of the mamodo world. In order for the many mamodo to use their powerful spell books, they need a human partner. Kiyo is a brilliant but aloof 14-year old. Kiyo’s father, an archeologist, finds a mamodo child named Zatch unconscious in a forest. He sends the goodhearted Zatch to be his son's mentor. It is up to Kiyo and Zatch to discover this together. The unsuspecting Zatch and Kiyo must defend themselves against the ambush of mamodo-king wannabees.