After a sleep of twelve thousand years, the Demon Empire rises again to conquer Earth. Reideen, the colossal machine guardian of the vanished continent Mu, detects the dark force and awakens inside its golden pyramid, informing young Japanese boy Akira Hibiki that he is the sole heir of Mu who must aid Reideen in saving the planet in the shadows of forgotten deep temples.
He receives help from friends, the spirited girl Mari Sakurano—daughter of a scientist battling the Demon Empire—and several teammates from his high‑school soccer squad.
