Rising from a hurled volcanic rock, Godzilla, it seemed, had once again returned to his malevolent ways. Waging a campaign of destruction against humanity, this fake Godzilla leveled anything that stood in its path. Not even Anguirus could stop its power. The quadruped reptile, though, being able to see through the hidden MechaGodzilla's disguise was powerless to halt its wrath. Receiving a grisly broken jaw, the kaiju was forced to flee, leaving the fake Godzilla to once again push deeper into Japan's mainland.

By nightfall the machine had arrived at a refinery. Using its golden hued flamethrower breath, the demon set the area aflame. Unfortunately for it, though, the real Godzilla had sensed its presence and came forth to battle. Fighting with fierce determination, the real Godzilla tore and blasted away chunks of the doppelganger's rubber skin. He was perplexed by the unusual affect his attacks had against the foe, but his questions were soon to be answered. The Black Hole aliens, which had constructed this hellish instrument of terror, burned away the guise and revealed to Godzilla and the world the true Mechagodzilla.

With gleaming ember eyes and radiant armored skin, Mechagodzilla wasted absolutely no time in proving its power. Following its commands, the titan immediately unleashed waves of finger rockets and laser eye beams. Godzilla was tossed for a loop and thrown to the ground like a child's toy. Never had the giant ever been assaulted with such force. Yet silent rage burned in his being, and the reptile stood again to fight. Answering Godzilla's sea blue nuclear breath, the machine unleashed its eye beams. Both godly forces struck, pushing back and forth; however, only one outcome was possible. The cosmic forces exploded with ear shattering force, knocking both competitors to the earth. Godzilla fell into the bay, leaving only a churning swirl of blood to mark its presence, while Meachagodzilla suffered major damage to its head control unit, forcing the aliens to recall and repair their war machine.

Recalling it back to their Okinawa base, repairs on the robot became time consuming. So, to hasten the problems, they forced a human scientist named Hideto Miyajima, whom who had some knowledge of the alien technology, to fix it. A few days passed before they launched their weapon once again. This time, though, humanity was prepared. Awaking the legendary protector god, King Caesar, the prophecy, carved in the Azumi Royal Family's cave that told of an epic war, was becoming a reality. The two monsters fought heatedly, but not even the giant golem like kaiju could overcome the metal warrior. Giving ground, it looked as if the god like creature was to be defeated, that is until Godzilla broke through the bay's surface. Marching inland, Godzilla seethed with a madding fury. Turning the conflict now to a two on one, it wasn't long before the monsters were able to overcome the omnipotent strength of the machine. MechaGodzilla exploded into countless pieces of shrapnel after Godzilla had torn off its head, ending the alien's plans for the time being.

Lead alien commander Mugal easily saw the reasons for why his race failed the year before to conquer Earth. The machine needed to be modified not only in weapons, but in how it worked. Hand controllers from several different operators were too slow to function effectively in hand to hand combat. Learning of the famed scientists, Doctor Mufuni's invention to control animal's brain cells, he sought an alliance. Only after did Mugar's men save the scientist's daughter, Katsura, did the ape like alien push forward with his plan. Placing the control device within the beautiful young girl, he gave the machine the ability to have the reaction time that of a real animal. Thereby eliminating it's one and only true weakness.

Along with the biped dinosaur Titanosaurs, Mechagodzilla was sent to obliterate Tokyo. Countless buildings crumbled, and humanity ran terrified, as the duo giants wade deeper and deeper into the city. All hope was nearly extinguished before Godzilla suddenly appeared. Fighting with all its heart, not even Godzilla had the strength to overcome two adversaries. It wasn't until mankind stepped in, with their secret weapon, did the odds become even. Using their super sonic wave oscillator, the humans kept Titanosaurs writhing in agony, thereby leaving Godzilla the opportunity to face his demonic twin alone. Rushing forward, the nuclear giant ripped the machine's head off as he did before. Unfortunately, this proved to be an almost fatal mistake. Housed in the bionic brain that was revealed beneath, was a horribly powerful laser beam weapon. So strong was this upgraded mechanism, that one blast was more than enough to topple Godzilla. It wasn't until Katsura gave way to the feelings of love and compassion did war the see an end. Killing herself in self-sacrifice, Mechagodzilla no longer had a controller to order it around. Godzilla wasted no time for the machine to completely power down and hurled the machine several miles with a powerful shoulder toss. Then Godzilla unleashed a final blast of his nuclear beam that resulted in the machines detonation. Exploding into a million pieces, Godzilla won against the aliens for a second and final time.