Undyne, Red, Mettaton and Sans were blown away into toppled buildings, while Jay was blown to another faraway building and crashed there.
The jet that had Dr. Gutierrez and the nfd unit spotted the bright object that was Jay. "Over there! Head towards that building!" Dr. Gutierrez exclaimed, and the nfd unit piloted the jet where Jay had crashed in the building. Once they landed inside the building, Dr. Gutierrez took off his seatbelt and climbed down from the jet quickly. He ran over to the bright-crystallized dragon, who he was certain that he was his son, once he spotted him. "Jay! Are you alright?" Dr. Gutierrez said, stopping a bit to shield himself from the heat emitting from the body. When the crystallized body of Jay heard his father's voice, it immediately raised its head and body up. At the same time, Jay's body shone bright until he returned back to his normal self. "Father?" Jay asked when he opened his eyes.
"Oh, thank goodness you're alright!" Dr. Gutierrez said in relief. He reached out to help Jay up to his feet, but flinched and retracted his hand when he touched Jay's arm because it was blistering hot. Jay had to stand up by himself. Once up, Dr. Gutierrez noticed something was worrying his son.
"I don't understand. Why can't I remove its core?" Jay asked. "Because it's impossible. If the positive and negative core energies make contact with each other, they cancel each other. And if their energies are pushed against each other by force, well...both will be destroyed." Dr. Gutierrez explained to him. Jay's eyes widened when he heard that, then turned to see where the colossal mechanical dragon was. It was slowly recovering from the energy blast made by the energy cancellation.
"Come on. We will go somewhere safe and I will devise a plan to create a machine, strong enough to separate the core from that thing." Dr. Gutierrez said as he placed a hand on Jay's shoulder and began leading him to the jet.
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The four monsters had fully recovered from the blast and were now searching for Jay once again.
Yet, before they could continue further, the mechanical dragon came around the buildings near the four monsters and targeted them.
Undyne and Mettaton began shooting at the mechanical dragon with their attacks and shots, telling Red and Sans to flee while they drew its attention. The two that were told to flee were a bit injured, which meant that they couldn't run too fast. Undyne, noticing this, began to call out Jay's name in hopes he could aid them in time as the metal dragon tore through the buildings.
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A sound of distress was heard, and Jay perked his ears up to hear where it came from. He walked over to the edge and stopped there, searching frantically with his eyes. Finally, he spotted them, all fleeing from the colossal metal dragon. Sans and Red were noticed limping a bit from small injuries inflicted. Then he realized that they were not going to make it as the mechanical dragon drew closer and closer to them while toppling buildings. If he didn't do something quickly, his friends would get crushed by the buildings.
"I have to go. My friends need me." Jay said as he got ready to fly with his mind already set on what he was about to do. However, his father stopped him by grabbing his hand.
"No! It's too dangerous! If you try to remove it again, there is no guarantee that you will survive." Dr. Gutierrez said to him sternly.
"My friends have no time. I have to save them!" Jay said pleadingly. Still, Dr. Gutierrez didn't let go of his hand.
"Don't do this!!! I....I don't want to loose you...again..." he said, his eyes starting to well up with tears. Jay, noticing this, gripped his father's hand a bit tighter and smiled a bit.
"It's alright. Don't worry about me. Because I'll find a way to come back. I don't know how, but I'm certain that I will. See you on the other side...dad." Jay said to his father before letting go of his hand and dropping off from the edge.
"NO!!!" Dr. Gutierrez yelled as Jay fell down to the ground. Right before he was too low to pull up, Jay concentrated hard and turned back to his other powerful crystallized form. Then, he streaked towards the mechanical dragon at high speeds.
The colossal metal dragon looked up and stopped chasing the four monsters on the ground. It spotted Jay and flared out it's wings and roared challengingly, ready to fry the small and bright fly that was headed its way. However, Jay was not interested in continuing the fight. Rather than that, he was planning to end it.
[All I need to do is destroy the core. Now the best place to do it is...] Jay said, looking up to the sky. That moment, he knew exactly where to go with the mechanical dragon and the rouge Blitzer nfd.

Outer space.

So, charging all the strength and energy he had inside, Jay accelerated more towards the dragon. Once close enough, he dodged the powerful laser, flew under it, and punched both hands into its chest. Then Jay increased the thrust amount given off by his crystal wings, which became strong enough to lift the colossal metal dragon off the ground. Soon, it was being carried upwards by Jay slowly and then progressively faster as time went on.
Undyne, Red, Mettaton and Sans watched in awe as Jay used his maximum potential to lift the metal dragon up into the sky. They kept watching as Jay continued to lift it up until both were no more than just two red and blue dots in the bright blue sky.
Up in the atmosphere, Jay continued to push the mechanical dragon space wards, with no sign of stopping, as it tried to struggle free from the clutch of the small but powerful crystallized dragon pushing it towards outer space. And Jay didn't stop until both of them were far away from earth, far from even the distance from moon.
Once far enough, Jay detached his hands from under the metal dragon and flew a safe distance from it, getting ready to continue fighting and do what he planned: destroy the negative core regardless of being destroyed in the end.
The mechanical dragon let out an angry roar and flared its wings, the two of them becoming metal tendrils that shifted and changed constantly. It launched them at Jay while simultaneously firing its powerful laser and missiles. Jay accelerated forwards across the star-decorated space, rolling, dodging, stopping to block, and turning as he continued towards the colossal machine.

Before getting close, he used his sword and powerful homing lasers to destroy and tare apart the structure of the metal dragon each time he passed by close to it. The energy flow was started to weaken each time it was hit, Jay felt, and soon the parts became weak.
Taking his chance, Jay aimed everything he got at the weak spots, destroying them. Large and massive explosions burst, sending every single pieces of body parts of the mechanical dragon away until nothing remained. Nothing except the compact sphere of metal rubble that the rouge Blitzer nfd has built around itself. Now it was exposed, with nothing to cover or protect itself with. Spotting it, Jay shot towards it and pierced the energy slot of the Blitzer nfd with his hand sword. The negative core got pierced a bit by the sword, but now it started to react again with Jay's positive core energy as it started to build up the cancelling reaction that would destroy both.
["WHAT......WHAT ARE YOU...?] the Blitzer nfd croaked out as it glitched painfully.
"I am not a machine, nor a monster or anything. I am..." Jay said to it as the light of the reaction build-up began to shine brighter and brighter.
As that happened, time seemed to slow down. Memories of his flashed in front of Jay's very eyes, those about his most happiest moments with his friends, the hard challenges he faced, and the moment when his father reconnected with him. Those things were enough reason for him to give his life so his friends could have a better future. And he didn't regret it a single bit.

"I am......human."

In a blinding flash, both were consumed by the blinding reaction blast light that shone brightly in space.