They'd been beaten back one by one, every single time they'd tried to take that pitiful blue planet. Yes, it seemed unbelievable that such an insignificant spec on a cosmic scale could defeat mighty conquerors such as them, but yet it had happened. The alien invaders had had enough. It wasn't a simple matter of conquering the planet, now it was a matter of pride. And revenge. Even the forces of Seatopia had joined this coalition, contributing Megalon to their forces. But they had to come up with a new plan. Attacking all at once wouldn't help. The Kilaaks had tried an all-out attack and it hadn't worked. So instead, they'd divert the Earth defenders from their true goal with other attacks. And first up would be the team of the Star Hunter Nebula M and Black Hole Aliens.

In Osaka, the citizens went about their normal lives, knowing a kaiju attack was possible, as always, but that was the last thing on their minds. They had other things to do besides worry... But perhaps they should have. Suddenly, the sound of rocket engines filled the air, the powerful Super Mechagodzilla descending from the sky with a mechanical screech. But this wasn't the same one they knew. The Black Hole Aliens had seen the superiority of the Earth Mechagodzilla's arsenal over their own when dealing with Earth kaiju and duplicated it. The only difference was that theirs was controlled remotely as their original had been. That and Earth metals were easier for them to use, their supply of Space Titanium having fallen into the black hole along with their homeworld. What surprised the Earth people more than Super Mechagodzilla assaulting a row of buildings with its Mega-Buster and Garuda cannons was Gigan descending from the sky with a screech, landing next to Mechagodzilla and obliterating a building with his cluster beam.

The twin terrors unleashed their combined weaponry on the surrounding area, sending plumes of smoke and fire high into the sky. It seemed nothing could stop the twin tyrants, until Gigan noticed a man staring at him from a nearby building, instead of running. This surprised the giant, humans were normally more panicky than this. His hesitation allowed the man to pull out a tiny object from his coat and point it skywards. Suddenly, Gigan was startled by a blinding flash of light. When the flash finally faded, the cyborg monster was even more surprised to be face to face with the heroic giant known as Ultraman!

Ultraman was quickly on the offensive and delivered a karate chop to the side of Gigan's cranium, staggering the space monster and allowing Ultraman to duck down, grabbing Gigan's legs and pulling them out from under him. Gigan crashed to the ground with a startled screech, screeching even louder as Ultraman grabbed him by the legs and spun around, lifting the cyborg off the ground and spinning him around several times before releasing him. Gigan went flying and slammed hard into the ground, screeching in pain. Super Mechagodzilla noticed its ally had been attacked and quickly opened fire on Ultraman with its Mega-Buster and shoulder cannons. The giant hero noticed this and quickly raised his hands, putting up an energy barrier, allowing the cascade of energy to flow over the barrier and disperse harmlessly. Before another barrage could be fired, Ultraman leapt high into the air and delivered a flying kick to Super Mechagodzilla's chest, knocking the mecha backwards. Ultraman followed up by charging forwards and grabbing Mechagodzilla by the midsection, lifting him up and spinning around, driving the robot hard into the ground, sending sparks flying from its body.

Ultraman stood up to look over his opponent and see if enough damage had been done. This allowed Super Mechagodzilla to spin its head up and fire a blast of yellow energy from its eyes, striking Ultraman in the chest and causing him to stumble back. Ultraman suddenly cried out in pain as a sharp hit landed on his back. Gigan had regained his senses and slashed Ultraman across the back with his scythe-like hands. Before Ultraman could recover, Gigan swung his tail around and clamped the claw-like object at its tip around Ultraman's neck from behind. Super Mechagodzilla managed to rise to its feet and unleashed a blast of its Mega-Buster and shoulder cannons into Ultraman's chest and gut, causing him to scream in agony. Once Mechagodzilla was done, Gigan swung his tail, sending Ultraman flying through a building. As the hero tried to rise, Gigan blasted him with his Cluster Ray, sending a cascade of explosions over the hero's body. Ultraman moaned, falling to the ground in pain. His Color Timer began to flash. He knew he didn't have much time left but he needed a chance to recover from the assault.

Gigan lifted Ultraman to his feet and held his weapons to the hero's throat, preparing to execute him. But just as he got ready to behead the warrior from the Land of Light, a snaking blast of electrical energy collided with Gigan's spine, causing him to shriek in pain and fall to the ground. Super Mechagodzilla turned to see Kiryu standing before the evil machine. The cybernetic war machine roared at the duplicate of his predecessor, Akane piloting the mecha from within. Before the alien robot could recover, Kiryu's missile pods sent an onslaught of rockets at it, colliding with Super Mechagodzilla's armor and sending the robot backpedaling. Gigan growled, standing back up. But before he could attack, Ultraman grabbed him by the tail, pulling him to the ground. The Ultra hero looked up and nodded to Kiryu, grateful for the help. He then proceeded to lift Gigan off the ground and throw him back down.

Akane looked at the replica Super Mechagodzilla, growling. "Let's show them what you can do, Kiryu," she said, unleashing barrage of lasers from Kiryu's wrist mounted cannons, bombarding Super Mechagodzilla. Akane realized too late, however, that Mechagodzilla's synthetic diamond coating absorbed the lasers as its Plasma Grenade port opened. Knowing what was coming next, Akane jerked Kiryu's controls sharply, forcing him to dodge as the enhanced energy blast erupted forward. Kiryu managed to avoid a direct hit, but his left laser gauntlet was blown off. Realizing those weapons where useless, Akane detached the other one, causing it to fall to the ground and free up Kiryu's right hand more. As Super Mechagodzilla opened fire with a Mega-Buster, Kiryu managed to evade it and fire another barrage of missiles, hammering the evil mech hard. This gave Super Mechagodzilla the chance to open fire with its shoulder cannons, blasting Kiryu in the chest and sending the cyborg staggering back, before firing another volley of the Garuda cannons, blasting Kiryu to the ground.

Ultraman dodged several slashes from Gigan, responding with a strong kick to the side, causing the space monster to stagger sideways. As Ultraman attempted another punch, Gigan opened ports on his chest and fired his razor disks, slashing Ultraman's sides, causing the alien hero to cry out in pain as light surged from his wounds. However, Ultraman was smart enough to realize the blades were coming back around, quickly spinning around and crossing his arms in a plus shape, firing the Specium Ray with expert precision, blowing both out of the air. Gigan suddenly took to the sky, his buzzsaw coming to life as he dove past Ultraman, slashing his shoulder and toppling him to the ground. Gigan spun around and landed, raising his blade, once again preparing to behead the hero. Ultraman realized his Color Timer was flashing rapidly. He had to finish this soon. Seeing Gigan coming, he formed an Ultra Cutter and threw it straight at the cyborg. Gigan was taken off guard, allowing the blade to pass through his raised wrist. Gigan screeched in pain as his scythe fell off, clanging to the ground. Gigan stared at his stump in surprise and pain, the exposed machinery sparking. Ultraman quickly closed the distance and grabbed the stunned space monster by the throat, flipping him over his shoulder and smashing into the ground.

Kiryu managed to recover from the barrage of energy blasts and regain his footing. Akane pressed several buttons in the cockpit, causing Kiryu to fire his shoulder missile batteries like huge rockets. Super Mechagodzilla's rockets kicked in, allowing it to fly up and over the twin rockets, making them explode in the distance upon collision with a building. But they were merely a distraction. Super Mechagodzilla was suddenly caught off guard by Kiryu leaping high into the air and slamming into him, sending the mechanical Godzilla plummeting from the sky into the ground. Kiryu landed and, unhinged from his heavy weapons, moved at high speeds and was on top of Super Mechagodzilla before the machine could recover, raining blows into his opponent. Super Mechagodzilla's systems began to flicker, forcing its masters to think quickly, managing to raise its Garuda cannons and blast Kiryu point blank in the face, blowing off part of the faceplate to reveal the machinery beneath. As Kiryu was forced back, Super Mechagodzilla got to its feet and fired its eye beams, shoulder cannons and Mega-Buster all at once, bombarding Kiryu in a storm of energy blasts, tearing sections of armor off and exposing circuitry. When the assault ended, Kiryu emitted a low, mechanical screech and fell over, crashing through a building.

Ultraman forced Gigan to his feet and gave him another shoulder toss to the ground before jumping back as Gigan started up his belly saw to momentarily drive him away. Gigan quickly regained his footing and slashed at Ultraman, forcing him to jump backwards to avoid damage. This allowed Gigan to fire his cables on his remaining arm, wrapping around Ultraman's throat, choking him. He then began to pull Ultraman in, starting up his saw, preparing to slice the hero to ribbons with it. Ultraman struggled against the cable in an attempt to free himself. His life-force fading, he knew he had to do something. Inches from the saw, he suddenly crossed his arms and fired the Specium Ray point blank in desperation. The beam hit Gigan in the face, engulfing his head in a large fireball. Gigan's saw stopped spinning and he stopped retracting his cable, arms going limp as his decapitated corpse fell to the ground. Ultraman panted in exhaustion, untying himself from the now limp cable. It was then that he noticed what was going on with his ally.

Super Mechagodzilla lowered its arms, locking onto Kiryu's chest, preparing to unleash the G-Crusher and fry the cyborg's systems. The cables launched from the mecha's wrists, firing through the air... but they didn't meet their intended target. Ultraman dashed into the path, puffing out his chest to allow the G-Crusher to collide with him, discharging electricity throughout his body until Ultraman easily yanked them out himself. The hero had a history of resisting electrical attacks. Many of his foes had tried before and Ultraman had simply ignored it. The G-Crusher was no different. Ultraman brushed his chest off and flexed, the act surprising both the mecha and its controllers.

Akane managed to redirect the controls, rerouting them and allowing Kiryu to reactivate, thanks to Ultraman taking the hit for them. Kiryu rose to his feet and nodded to Ultraman, glad for the help. The mecha seemed to roar with a mind of his own, conversing with the hero, who nodded in reply. Super Mechagodzilla suddenly let loose with its cannons, trying to catch them off guard, but Ultraman shielded both of them with an energy shield. After the attacks cascaded off, Ultraman formed another Ultra Cutter and flung it, cutting the cannons to the Garuda unit off. Before Super Mechagodzilla could react, Ultraman lowered his shield and fired the Specium Ray. Even the hero's most powerful attack was simply absorbed, allowing the Plasma Grenade port to open in preparation... and fall right into their trap.

Akane, despite being surprised that Kiryu had conversed with Ultraman on his own, followed the plan displayed on the monitor. While Ultraman unleashed the Specium Ray, Kiryu had moved in closer, morphing his hand into a drill. The spinning appendage designed to cleave through Godzilla's flesh tore through the more fragile piece of machinery and into its inner workings, destroying the weapon right as it was about to fire. Realizing this would leave the energy inside Mechagodzilla no where to go after having already pressed the firing switch, Akane had Kiryu fall back, right as a large explosion tore out the abdominal region of Super Mechagodzilla, sparks and small fires coming out of the gaping hole. The mecha's eyes flashed and it roared randomly, flailing its limbs, malfunctioning from the massive amounts of damage it had taken.

Knowing they had to prevent the Black Hole Aliens from savaging their weapon, Akane armed Kiryu's ultimate attack. "Fire Absolute Zero Cannon!" she ordered, pressing the fire button. Kiryu's chest split open, blue energy collecting in the opening until finally, a surge of blue white light erupted out. Super Mechagodzilla was struck with a powerful force, a huge flash of light occurring as a pillar of ice went up around it, trapping Super Mechagodzilla in a small glacier. Kiryu roared and stomped his foot, causing the pillar of ice to crumble, reducing the once proud war machine to nothing but frozen dust.

Ultraman turned to Kiryu, the two both very low on power. The sentient cyborg and cosmic hero both nodded to one another in mutual respect. Kiryu's eyes faded as his battery ran dry, but Akane stepped out on his shoulder, saluting Ultraman. Ultraman nodded in reply, happy to have an ally. Ultraman looked up at the sky and held his arms upwards. "SHUWATCH!" shouted the Ultra, taking off into the sky and flying off, heading off to recharge as Akane watched on.

Up in space, a saucer floated above Earth, looking on. "Well, well. They failed. Too bad. Still, that wasn't our prime object," announced a female voice. "Alright, time for our next target," she said, letting out a laugh as a pair of ships flew past towards Earth.