Description: For years, Seatopia, the undersea civilization, has been heavily affected by nuclear testing conducted by the surface nations of the world. Upset by this, they plan to unleash their civilization's god, Megalon, to the surface to destroy the world out of vengeance.
On the surface, an inventor named Goro Ibuki, his kid brother Rokuro and their friend Hiroshi Jinkawa are off on an outing near a lake when Seatopia makes itself known to the Earth by drying up the lake the trio was relaxing nearby and using it as a base of operation (unknown to our heroes.) As they return home they are ambushed by agents of Seatopia who are trying to steal Jet Jaguar, a humanoid robot under construction by the trio  ... of inventors. However the Agents's first attempt is botched and they are forced to flee to safety.