Ok well, I'm back in a weeks time for this update- yay! I kept to a schedule! Now, to whomever is currently reading this, to your joy or disappointment I've decided this fic is going to have at least ONE MORE CHAPTER.

I REPEAT: THIS WILL AT LEAST BE A THREE-SHOT.

As you can probably tell, I'm trying for weekly updates so we'll see how long that lasts. It turns out I'm liking this concept a lot more then I thought (which was a lot to begin with) and even though I know how I want it to end, I've decided it's going to take longer to get there. Hence becoming a longer fic. Enough of my rambling, however I am sorry in advance for the cliffhanger I am leaving you with.
Pneumonia

Gray couldn't believe his eyes. Or his ears. In fact, he couldn't believe any other sense that was functioning right now for one very reason.

He didn't want to believe what his own senses told him.

Like pieces to puzzle he understood, but his still refused to get his head around what just might be his undoing. After all, he didn't know whether it was the screams, the claws, the horns or the wings that first caught his attention because the only thing he could remember was the last thing his dad ever said to him.

"E.N.D. is a flame demon."

The thought, like a mantra, kept repeating in Gray's head as he watched the spectacle before him, as frozen as his magic to react in any way possible. He had been so certain, so devastated and so full of revenge that he swore he would be the one to destroy E.N.D. with the Ice Devil Slayer Magic his dad gave him in his last dying breath and yet… now all Gray could think was – why him?

Why did the responsibility of killing his closest friend rely on him?

The days long ago that consisted of group jobs and friendly rivalries all seemed like a dream compared to this agonizing reality. Gray had guessed, somewhere in the deep recesses of his mind, that no matter what they would always be the victors, make it out alive with a happy ending. After all, their guild was Fairy Tail – the guild that obeyed no one and never gave up – the guild that nurtured dreams and stood for all that was good in this world.

That's the very reason why Gray never considered that maybe for once in his life the thing he wanted most could also be his biggest regret.

Anger and despair swirled in his mind, clouding his thoughts to the point where he wished he could just close his eyes and shut his senses from the events currently happening. But he couldn't. Gray knew that. Somehow he knew this very moment in time would be a factor in the future of many people, good or bad, and greatly influence upcoming events.

Despite that, all he could remember is his father's final goodbye and the promise he swore to fulfil. Gray was torn between two loyalties he neither wanted to break nor keep.

After all, how could Natsu be E.N.D.? The Natsu he knew since he was a kid, the one he laughed, bathed, learned, fought and played with- how could he be a demon over four hundred years old? Not even just any demon- Zeref's strongest demon?

Absentmindedly as the last of the screams rang in his ears, his left hand traced over the mark the Ice Devil Slayer Magic made on his right arm.

I might be one of the only people capable of killing E.N.D.

The thought shook his being to the very core, knowing he could be the other outstanding factor in all of this whose responsibility it falls onto in the end to make the ultimate decision.

With all Gray's heart he wanted to avenge his dad's suffering and honour his memory by killing the demon his father vowed to but was never given the chance. Even so, Gray didn't know if he would be able to kill a friend all the same.

It was Igneel that finally snapped Gray from his thoughts, alerting him that this was no time to think but to act. As the ground shook with Igneel's hasty landing Gray bounded closer to Natsu- or should he say E.N.D.- where Lucy also kneeled with tears streaking down her guilt-ridden face.

As he reached her, he was about to ask what exactly happened to see if there was any way to reverse it- because as Gray thought about it more, he realized as long as Natsu was Natsu there was no E.N.D. and he considered that just as good as dead if it meant he didn't have to kill a friend. But, he never got the chance.

Achnologia- of all the things could have happened this very moment- dove towards them with a fearsome roar. A shockwave thundered throughout the immediate area and both Gray and Lucy were thrown a few feet further back with the force.

As Gray recovered as quickly as possible, he was only able to catch a glance of Natsu getting up to face Achnologia's oncoming assault as Lucy groaned in pain next to him, and Gray noticed she had landed wrongly on her arm, most likely breaking the bone. He cursed silently, knowing that there were too many things happening at once for these events to not be considered a stream of chaos.

Just as Gray turned to look back towards Achnologia and Natsu, he watched as Natsu used his newly received wings to bound into the air that caused another shockwave of the same strength. However, this time, Gray managed to keep himself and Lucy grounded by using his ice to bind them in place.

No matter, he could only stare in awe as the Dragon and Demon collided with a force so strong the ground beneath them began crumbling and shifting. Once again Gray shielded himself from debris, and when he looked back he couldn't believe what he saw.

The very fact of having been trapped on Tenroujima for seven years because of Achnologia seemed preposterous to him now, as he watched the very same dragon shriek in pain one of it's wings was sliced clean off. Gray didn't know how that was possible; much less believe that it was Natsu whom had done it.

That was the event that finally convinced Gray that E.N.D. really was Zeref's strongest demon, as well as the fact that somehow Natsu was E.N.D.

The cold chill of realisation finally took over his senses as it settled into his bones. Even with his newfound magic, Gray couldn't ever believe to defeat a demon that could do that to Achnologia in one hit.

He numbly registered the terrible roar that shook the air as Achnologia tumbled towards the earth. Igneel leapt once more into the sky, done so more carefully than should have been possible as a breeze was the only factor towards warning Gray of the Fire Dragon's ascent. Upwards Igneel rose, sending a torrent of flame directly into Achnologia's flailing form.

Another terrible roar sounded incredibly pained, and Gray assumed it was once again Achnologia making those terrible sounds. Although Gray couldn't see anything but darkened forms through the massive torrent of flames engulfing the air above him, he had a feeling Igneel would handle the rest. He also couldn't be more grateful- despite how it had occurred- to see the terrible black dragon pay for its crimes against everyone he held dear.

Sighing, he just managed to refocus his attention as Natsu dropped fiercely to the ground causing another shockwave to tremor throughout the earth. Even from the distance at which the pink-haired Etherious stood, Gray could see the red tainted skin and claws dripping crimson onto the lifeless earth. Behind the form, a thunderous boom occurred as a black wing fell onto the earth.

A shiver ran-through Gray's body as he saw the once so-charming smile the dragon-slayer wore was now tainted with malice and flashing canines in a dreadful way Gray never imagined to see on his friend's face. As Natsu shifted the angle in which he stood, Gray finally saw his eyes. Despite the shivers wracking Gray's frame, a deep chill settled in his bones as he managed to see the very manifestation of immorality reflected in Natsu's onyx orbs.

Gray gripped his fist and let loose a breath he'd been holding. The figure ahead of him was not Natsu, even though it wore his face. It was no longer the friend he had hoped it was, it was no longer the rival he used to quarrel with. It was no longer his best friend that stood before him.

He had made his decision. He had decided his loyalty. He would be the one to save them all from the threat that they now encountered.

As he began to stand up, Lucy looked towards him as if pleading with her eyes for him to bring Natsu back. Gray knew how she felt. There was nothing in the world he wanted more at the moment then to see his best friend in the place of the demon that now wore Natsu's body like a disguise.

But alas, Gray felt it, a dread like no other take its place deep in his heart as its new home. In that dread a thought was buried that Gray didn't want to believe, but all the while he had a feeling he couldn't change it. This thought contained the solution to his current predicament. It told him that there was only one way to bring Natsu back.

Tears stung his eyes and they dripped from his face onto the ground below. There was no other way. He was the one given the responsibility by his father. He would keep his promise. He would do what was right.

He had to kill E.N.D.

… Even if it meant killing Natsu Dragneel.