After lying dormant for 12,000 years, the Demon Empire resurfaces to conquer Earth. Reideen, the colossal robot guardian of the forgotten land of Mu, stirs from its slumber in a golden pyramid, choosing young Akira Hibiki as the sole descendant of the ancient Mu civilization destined to aid in Earth's salvation. With the support of his comrades, including Mari Sakurano, the lone female companion and daughter of a scientist battling the Demon Empire, and his high school soccer teammates, Akira embarks on this epic quest.