Young Akitsu Masato is seized by a covert government initiative called "Last Guardian." He learns that his ordinary student life was fabricated and that he is destined to steer a colossal machine named "Zeorymer of the Heavens." The reality hits him when he witnesses his parents receiving money for raising him. "Last Guardian" is gearing up to revive "Hau Dragon," a faction determined to dominate the world. Fifteen years earlier, Hau Dragon constructed eight massive robots, each embodying a natural force. Yet before any could be deployed, their creator Kihara Masaki annihilated all but the chief unit: Zeorymer. He transported Zeorymer and an embryo to state hands, and the embryo grew into Masato. Today Hau Dragon has reassembled the remaining seven mechs and seeks the final one. The fate of Zeorymer lies with Masato and Himuro, who must confront Hau Dragon, though neither of them is as they appear.