In college studying archaeology, Dai Sawamura deciphers the figures on the Nazca Plain in Peru. Impressed by this feat, the Galactic Union Police (銀河連邦警察 Ginga Renpō Keisatsu?) recruit and train him to be Earth's third Space Sheriff. He is given the code name 'Shaider' in memory of an ancient warrior who defeated the villain Emperor Kubilai and brought down the Fuuma 12,000 years ago. When the Fuuma returns, Dai is deputized as he returns to Earth to battle the Fuuma.