Aliens intend to take over the planet and, just in case Godzilla tries to interfere, have built a mechanical version of him to put an end to his interference. The Earth humans summon the legendary King Seesar to assist Godzilla in the battle.

In response to Japan's request for a countermeasure against Godzilla, UN engineers construct Mechagodzilla, a giant robotic version of Godzilla. Nonetheless, Godzilla proves himself a force to be reckoned with against this monstrosity and battle ensues