The Doron Empire, originating from the Ganymede System, targeted Earth as a prime world for subjugation. This expansionist drive was ignited by the ambitious General Ozmel, who usurped Queen Medusa—the reigning ruler of the Ganymede System—kicking off a universal conquest.
Earth teeters on the brink of defeat, having nearly fallen to the empire. In its final days, one scientist, Dr. Shikishima, pins humanity's last hope on a colossal mecha: the Mechander Robo, specially built and programmed to fight off the alien invaders and prevent a complete takeover. To pilot this formidable machine, Dr. Shikishima enlists three individuals—the enigmatic Jimmy Orion, his own son Ryosuke Shikishima, and Kojiro Hachijima.
While the core narrative revolves around Earth's struggle against the Doron Empire, lead pilot Jimmy Orion harbors a personal history that ties directly into the larger storyline.