Hey everyone, this is my first fanfic so...enjoy!

P.S I apologize for any mistakes I make in advance.

Sans stood in the judgement hall waiting for the human for what seemed like his hundredth time.

Wait, no. It was probably well over the hundredth mark.

In all honesty, Sans was getting tired. Tired of fighting a battle he knew he couldn't possibly win. Every time the barrier was broken and monster kind made it up to the surface, it was all ripped away in an instant.

Sometimes, the human wouldn't reset immediately. The first time that happened, Sans immediately began to get his hopes up. But, after one week, he opened his eyes only to be in his room back down in Snowdin.

The second time it happened, Sans didn't get his hopes up until two weeks had passed. But, after a month, he was back down in Snowdin again.

It was a loop. Every time they got to the surface, Sans would wait for the next reset to occur. Sometimes it was immediate. Sometimes the human would let them enjoy their freedom for a bit before resetting again. After what seemed like the hundredth time of getting up to freedom but having it ripped away from him, the surface wasn't really appealing anymore. But, Sans could live with it. Down in the underground, they had all they needed. Good food, nice friends, and bad laughs. And through each run the human did, they never harmed anyone. Though they took away their freedom each time, they had never harmed a single soul. And Sans was okay with that.

But, then they started hurting others.

It had started with only one or two monsters each run, just to satisfy their curiosity. But then, with each run, it had become more and more. Some runs they would only kill select monsters, other runs they would kill everyone but those select monsters. But, they weren't satisfied yet.

And that's when the genocide runs began.

Sans just stood there as he saw monster after monster being slaughtered. But, he didn't lift a finger to help them. After all, it would all just be reset again and again. But then, the human came to his brother.

He watched as his brother showed mercy to the human and watched as he offered a hug to them.

He watched as the human stepped into his embrace and watched as a wicked smile graced their features.

Sans wanted to cry out, wanted to stop the human, wanted to do something.

But he just stood there, still, as the human whipped out their knife and turn his brother into dust.

At that moment he knew something had to be done.

So Sans went to the judgement hall and waited. He waited for the human to come. And when they did come, he fought. He fought with more effort than he thought he had. And he told them he knew, about the timelines, resets, their determination, but never saying that he could remember.

And then he died. The human had killed him. After hundreds of resets and deaths, the human had finally beaten him. As he closed his eyes waiting for the inevitable to happen he suddenly felt something soft beneath him. That was the moment he realized the human had reset again.

After the first genocide run came many others. Each time the human would go through the underground killing every single monster while Sans did nothing to stop them. And each time Sans would confront them at the judgement hall and do the same song and dance he had been doing for hundreds of times now. But, he couldn't take it anymore.

Now, as he stood in the hall waiting for the human to come, he knew he couldn't just not care anymore. For the sake of the whole underground he had to something because he was the only one who could. (Sans supposed you could count Flowey, but that weed would probably help the human if they didn't kill him like everyone else every single time.)

Then, the human came, smiling from ear to ear. Waiting for the thrill of the fight to begin. Sans sighed as he began his usual monologue.

"let's just get to the point."

The human faced Sans as he spoke, anticipation clearly on their face.

"it's a beautiful day outside. birds are chirping, flowers are blooming. on days like this, kids like you…"

Sans eye sockets suddenly went dark.

" l"

And the battle began. Each time Sans would send out his attack and the human would dodge. Each time the human lunged at him with their knife, Sans would dodge. After what seemed like an eternity came the part Sans knew all too well. The part where he died.

But, he had a plan and it had to work. For the sake of the underground, it had to. Even if the timing was just one second off, the plan would fail.

" well, here goes nothing... are you ready? survive THIS and i'll show you my special attack!"

After that was said, Sans sent out his attack. Waves of complicated bone patterns flew towards the human. Gaster blasters shot at the human at blinding speeds. He attacked them with all he had. As usual, the human dodged them all with nothing but a grin on their face. Sans was breathing hard. He hoped he had enough energy for his plan.

"all right. that's it. it's time for my special attack. are you ready? here goes nothing."

The human's grin widened; it was almost the end of the fight. That meant it was almost time to kill the comedian. And the thrill of killing him never got old. After all, he was the only one that actually put up a good fight. They still remembered the first time facing off against him. They were so shocked at how easily he had been able to kill them. But, they eventually killed him like all the others though, some part of them was disappointed the fight was nearly at its end. He was the only fight that actually made them try. Oh well, they would just reset after this and fight him again.

"yep. that's right. it's literally nothing. and it's not going to be anything, either. heh heh heh... ya get it? i know i can't beat you. one of your turns... you're just gonna kill me. so, uh. i've decided... it's not gonna BE your turn. ever. i'm just gonna keep having MY turn until you give up. even if it means we have to stand here until the end of time. capiche?"

Sans knew it was almost time. He had saved just enough energy for his plan. Now, he just had to do his part and wait.

"you'll get bored here. if you haven't gotten bored already, i mean. and then, you'll finally quit. "

Sans hoped the nervousness he felt wasn't conveyed in voice. Luckily, one look at the human's expression told him that they weren't paying any attention at all to what he was saying. They were probably just waiting for the part where they could kill him. He continued on with his little speech.

"i know your type. you're, uh, very determined, aren't you? you'll never give up, even if there's, uh... absolutely NO benefit to persevering whatsoever. if i can make that clear. no matter what, you'll just keep going. not out of any desire for good or evil... but just because you think you can. and because you "can"... ... you "have to"."

The human just stared at him, their wicked grin still on their face. Their grip around their knife tightened and their stance shifted in anticipation.

"but now, you've reached the end. there is nothing left for you now. so, uh, in my personal opinion... the most "determined" thing you can do here? is to, uh, completely give up. and... do literally anything else."

After saying that, Sans let himself slowly "fall asleep". Well, that's would it would look like to the human anyways. What he was really doing was concentrating. He had to time his actions perfectly; any single misstep could lead to failure.

Suddenly, his eyes shot open and he dodged the human's blow.

"heh, didja really think you would be able-"

The human lunged again with their knife pointing towards Sans. Their face had an expression of glee on it. Finally, they got to kill him-

Ding

The human suddenly found themselves unable to move. They frowned in confusion. This wasn't supposed to happen.

"kiddo, you really need to learn when to quit."

The human was in shock. What was going on? Then it clicked. The only reason that things would happen differently is if Sans remembered. Then it hit them. Sans…he….remembered. They thought he just knew about the resets. They didn't expect him to remember everything. Then, they smiled and laughed. If Sans remembered everything, then it would so much more fun playing with him. Oh sure it was fun seeing all the monsters reaction to the things that they did, but every time they would forget. But Sans…it would be so much more fun playing with someone who could actually remember.

The human smiled their wicked grin and said, "Oh, Sansy, it's going to be so much fun playing with you now! I can't believe you never told me you could remember! Anyways, I think this would be a good time to reset now. See you in the next run."

Then, the human summoned the reset button. They brought their hand down on it and pressed it.

And that's when Sans fired his gaster blasters.

The beams hit the reset button, effectively destroying it. They looked surprised for a moment before looking at Sans.

"What? Was that supposed to do something?"

"yeah, it did."

"What do you mean? Nothing happened."

"try looking down."

The human looked down and was shocked at what they saw. Their legs…weren't legs anymore. They were pixels that were disappearing faster and faster. They glared at Sans.

"WHAT DID YOU DO?"

Sans didn't feel like answering that question. And surprisingly, it wasn't because they were a genocidal human. (Though, that would've been a good reason.) It was because it would be too complicated for anyone (except Alphys maybe) to understand. To put it simply without all the scientific gibberish, whenever the human reset, they would pull everything back to the start, including themselves. But, if Sans destroyed reset button while they were in the process of resetting, they would be put in a state of limbo. They would exist in the timeline but not exist at the same time. Because of that, they would get put in a place between timelines; a place that a certain former royal scientist had dubbed "The Void".

It had taken a lot of deciphering of his father's notes and lots more research afterwards, but at the end, it had all worked out. The human would be gone forever.

"NO!"

The human frantically tried summoning the reset button, but it was no use. Sans had destroyed it.. At that moment, they realized they were feeling something that they hadn't felt in a long time.

They felt scared.

And that feeling quickly turned into anger. Anger at that stupid comedian for ruining everything. They tried hitting him with their knife, but Sans quickly dodged the incoming blow.

"WHY DID YOU DO THAT?"

"well, i guess you could say that i was tired of your resets and your genocidal runs through the underground, so i decided to do something about it."

"I THOUGHT YOU DIDN'T CARE ANYMORE!"

"let's just say after seeing all of my friends and my brother die in front of my eyes more times than i can count, i decided to do something about it."

The human had a stunned expression on their face before turning into a different one.

Desperation

"SO WHAT? EVERYONE IN THE UNDERGROUND IS DEAD! NOW THAT YOU'VE DESTROYED THE RESET BUTTON, THEY'LL BE DEAD FOREVER!"

"you'll be surprised at what the right amount of DT can do."

"WHAT? HOW?"

"you'll have to thank my father for that."

The human opened their mouth to speak but found they couldn't; the pixels had gotten to their face. With one last glare at Sans, the human dissolved into pixels and vanished.

Sans breathed a sigh of relief. It was over. Even though monsterkind might not ever make it to the surface, at least they wouldn't have to worry about genocidal humans anymore. Sans thought about how was he going to revive everyone. He had read his father's notes, but there were hundreds of monsters living in the underground. It would take a while. Maybe he could revive Alphys first and have her help out-

Wait

While he was in his thoughts, something caught San's eye. The columns in the judgement hall were turning into pixels. Sans would've frowned if he could. Instead, the comers of his smile tightened. What in the name of Asgore was happening?

Sans was confused. This defiantly wasn't supposed to happen. He had read all the notes. None of them said that this would happen. He began to panic. What was he supposed to do? Suddenly he felt a small tingling sensation in his legs. He looked down and saw most of his legs had been turned to pixels.

No, no this couldn't be happening.

Sans quickly tried to think of anything that could reverse this, but his mind came up blank.

Whatever happens…just let me see Papyrus again.

And then he vanished.

Author's Note:

Disclaimer: I do not own Fairy Tail or Undertale.

Whew! First chapter is finally done! For all you Fairy Tail fans out there and wondering when our favorite wizards are going to pop up, don't worry. There'll be plenty of Fairy Tail in the next chapter.

I'll try to keep my updates regular but with school and all, there'll be no guarantees.

In the meantime, drop a review and tell me what you guys think of this so far, what you wanna see, questions, and ideas. Oh yeah, and any mistakes you see. That would be helpful. Really helpful.

So yeah, see you next time!