Hedorah was enjoying his new status as King of the Monsters. Ever since he'd melted Godzilla to a skeleton, life had been good for him. Humans were too terrified to deploy any of their mecha against him, knowing if they couldn't beat Godzilla, they'd be no match for the one that slew him. With little to no threat to him, he traveled freely, descending on cities and feeding on whatever he pleased. Today's menu: car exhaust. The Smog Monster sucked cars, drivers and all, into his body. His simple mind knew that he had little challenge to his awesome might anymore, so he could occupy himself with more important things, like eating.

However, the kaiju's thoughts where soon drawn from his meal to the sky by the roar of jet engines. He turned his blob-like frame around to see several massive jets lower mankind's latest creation before him, Kiryu. Hedorah was surprised, not by the similarity it had to the beast he'd slain in appearance, but in how he felt to his senses. He FELT like the former King of the Monsters.

Mankind had understood one simple fact: Godzilla was their protector and despite past attempts at killing him, without him, they'd realized how much they needed him. So they did the only thing they could - Build a cybernetic body around his skeleton, making his DNA into the bio-computer driving it. In essence, Godzilla was reborn as a mechanical savior, Kiryu. And in this battle, they decided to do something they'd rarely do otherwise... cut Kiryu loose. They didn't need to direct his actions, the bio-computer knew its new powers, and Godzilla's memory knew he was facing his killer. Surely, he would seek his revenge.

The mecha's eyes lit up. They had been momentarily yellow before, but without the restraining program, they turned red, the tear line down the side glowing the same blood color. Kiryu reared his head back and let out a mechanical imitation of Godzilla's roar, driving Hedorah back in shock and surprise, dumbfounded that somehow his old enemy had come back to life. Kiryu, Godzilla's soul begging for retribution and vengeance from within the cybernetic shell, quickly opened his maw, letting loose a swirling stream of thunder from his maser canons, striking Hedorah in the shoulder and discharging a high voltage shock. Hedorah screeched in agony as his amorphous form met the one of the few things it had no defense against, electricity. When the beam finally ended, dehydrated and dead flesh fell from Hedorah's body. Startled by his rival's new power, the Smog Monster quickly regained his composure and let loose his red eye beams at Kiryu, only for the cyborg to launch high into the air with his rockets and evade them.

Hedorah looked up quickly, trying to catch sight of his now airborne opponent... only to receive a flying kick to the face, toppling him to the ground with a surprised gurgling screech. Kiryu flew back to a safe distance and his missile pods sprung to life, sending an onslaught of missiles into the sky. Hedorah was pelted with explosives, blowing chunks of blazing flesh from his body, but rage more than pain filled his mind as he rose to his feet, sludge trickling in to replace the missing flesh. Hedorah rose up and fired a ball of sludge at Kiryu, striking his shoulder, but to his surprise, Kiryu merely marched forwards, swiping it off his metal skin, leaving a discolored spot, but nothing more than that. Godzilla's mind found itself grateful for one fact: he no longer felt pain. It'd make claiming his vengeance all the easier.

As Kiryu marched forwards, more blobs of sludge were launched, only to, just as before, be wiped off the metallic defender's skin. Finally getting in range, Kiryu extended a blade from his wrist, electricity crackling across it before plunging it into Hedorah's gut, discharging its energy into the Smog Monster. Hedorah screamed in agony, his body convulsing with electricity as it surged through his body, drying out and killing several million of the microorganisms that comprised him. In desperation, Hedorah unleashed his eye beams into Kiryu's chest, sending him crashing to the ground. He was quickly bombarded by more beams, sending shrapnel flying high into the air and exposing wires. Hedorah realized his position and fell on top of Kiryu, trying to dissolve the mechanical titan with his acidic body. Kiryu struggled, trying to free himself. Alarms were going off throughout his body as systems were put in jeopardy of being dissolved, memories of his previous death flashing through him. Kiryu finally managed to maneuver his tail around and drive it forwards, its tip penetrating Hedorah's eye. Hedorah screeched in agony and staggered off of Kiryu's body, his eye slowly closing as thousands of gallons of sludge poured out.

Kiryu rose to his feet, parts of his armor melted down to exposed wire and machinery. His tail tip was corroded down to the skeleton used as its framework and his electrifying blade was now reduced to an unrecognizable hunk of slag. But still, he could function, and that was enough. Kiryu armed his shoulder missile pods and sent them sailing through the air, plowing into Hedorah's chest and driving him backwards through several buildings with great force before they exploded, blowing a gaping hole in his chest. Hedorah, being merely a pile of sentient sludge, rarely felt pain from such attacks and transformed into his flying form, his eye still sealed shot from the damage. He took to the sky and rained down energy rays at Kiryu, blowing off large chunks of armor while trying to suffocate the armored titan with his sulfuric mist, but while it corroded his metal armor, Kiryu did not choke, for he had no lungs. Using the speed gained from shedding his missile pods, Kiryu launched into the air and roundhouse kicked Hedorah from the sky, sending him through a building. Hedorah, screeching in surprise, switched back to his adult form in time for Kiryu to land on top of him and rain blows down into his face. The cyborg took great pleasure in enacting his vengeance on his murderer, not caring that his hands sustained mild burns from contact with the corrosive kaiju. Hedorah finally managed a counterattack with a swipe of his arm, toppling Kiryu to the ground before standing up and swiping at his head repeatedly, discoloring metal as he pummeled the cyborg's cranium. Kiryu roared out in rage before firing his Maser Cannon, catching Hedorah in the shoulder and staggering him back, gurgling in agony. Kiryu's leg rockets powered up, launching out of Hedorah's way.

Hedorah managed to recover from the Maser Cannon attack and blasted Kiryu out of the sky with his eye beams, refusing to let up. He followed up with another barrage of eye lasers, burning into Kiryu's armor and exposing more sparking circuitry. Hedorah lumbered over and grabbed Kiryu's head, trying to force it into his acidic body, only for Kiryu to counter by driving his fist clean through Hedorah's body, but accomplishing nothing more than burning the armor off to the bone. But, as in life, he was still capable of moving it, allowing him to try and fight Hedorah's hands off his head, but leverage on the part of Hedorah prevented this from being possible. Kiryu soon realized this, and tried firing his Maser Cannon, only for Hedorah to clutch his mouth and clamp it shut, still trying to force him inside his body.

Hedorah gurgled in victory as Kiryu's cranium was forced into his chest, metal beginning to burn away in the acid at a rapid rate. But Hedorah's victorious roar soon turned to one of shock as he felt a cold sensation below him. Kiryu chest had opened, blue energy gathering in the Absolute Zero Cannon. Hedorah realized he was in trouble, and struggled, trying quickly to get Kiryu out of his body and evade, only for Kiryu to use the opportunity to get his feet underneath him and get upright, holding the Smog Monster in place. With a blinding flash of blue light, the Absolute Zero Cannon was fired, plowing into Hedorah point blank. Hedorah let out a loud screech of agony which was cut short as he was flash frozen by the cyborg's ultimate weapon, leaving the mighty tyrant nothing more but a hunk of ice.

Kiryu tore his head out of Hedorah's body, scattering frozen sludge in all directions. His head was badly burned, skull visible in some places. The left eye was burned away entirely, circuitry revealed almost everywhere around it. But within the skull, the bio-computer was still functioning completely, despite having sustained cracks in its form from the discharge of the Absolute Zero Cannon. The cyborg looked over to Hedorah's frozen body before he swung his tail around, shattering the Smog Monster to millions of pieces. He quickly looked through the rubble, making certain Hedorah was dead for good, knowing not to take him lightly. Sure enough, some wet sludge still lived inside, uniting into a much smaller flying form Hedorah, which tore free from the rubble, trying with all his might to get away to fight another day... Kiryu wouldn't let it be so easy. Unleashing his Maser Cannon, he struck Hedorah in the back, near the jets keeping him aloft, drying them out and sending him plummeting to the ground. Hedorah landed on the Space Needle, the point of the structure driving through the soft body of the Smog Monster, impaling him.

Hedorah screeched in agony, trying to free himself, only to fall silent when the reborn Monster King stomped over. Hedorah looked up into the face of the cyborg to find a terrifying sight. Through the eye of the skull, Hedorah saw flesh had emerged from the bio-computer, a pulsating brain beginning to form. Like any part of his body, Godzilla's brain was able to regenerate, and the cells grown to serve as the bio-computer's biological component were no exception. Slowly those cells had began to regenerate once air got in from the cracks in the casing of the shell surrounding them. Despite all odds and biological possibilities, Godzilla was regrowing inside Kiryu! But Hedorah wouldn't live to see the King of the Monster's return. Kiryu let loose a Maser Cannon blast into the Space Needle, using it like a conductor, sending thousands of volts coursing through Hedorah's body and Hedorah into a flurry of screams and convulsions until finally, the Smog Monster was nothing more than dust, finally dead for good.

Kiryu reared back his head, letting out a fierce, Godzilla-like roar. Slowly looking off into the distance where Monster Island was, an organic eye regenerating in place of Kiryu's lost one, his arm too beginning show muscle and blood vessels, organs regrowing and forcing internal robotics out of their way. It'd take weeks for him to regenerate, but it was clear there was no stopping it now. Hedorah was dead, and Godzilla had reclaimed his throne, and soon, his body as well.