The Smart Brain Corporation, the world's most powerful corporation, is trying to take over the world using Orphnoch, the next stage in humanity's evolution, to covertly kill off the human population. However, as endgame draws near, Yuusuke learns that there is a horrible revelation behind Kuuga and the Grongis' leader. It is up to Yuusuke, along with the assembled Science Police, to use the various powers of Kuuga in order to stop and defeat the Grongi Tribesmen from their continuous killing and ensure the happiness of others. In present day, a multi-talented man named Yuusuke Godai finds himself linked to the mysterious stoned belt that was found within the escavated cave as the Grongi are resurrected and resume their murderous game on the desandants of the Linto, humanity itself. Long ago, the Grongi Tribe terrorized the Linto until a warrior named Kuuga appeared and defeated the Grongi, sealing their leader within a cave.
