Till Death Do Us Part - Dust Sans x Reader

Chapter 1

It was a lovely day. The sun stood bright above the world; heat basking down on the citizens of this town. Trees swayed side to side in the small breeze as birds of all sizes flew about and sang their joyous songs. 
To most, this would be a peaceful day, one that many would enjoy going out in and enjoying themselves. Not you.
You found yourself on this summer's day trapped in your room, unsurprisingly, sitting at your desk. The curtains were drawn, blocking out any and all light. The only thing illuminating the room was the faint glow of your computer. 
"I've heard this game was supposed to be good, but the last time I trusted any sort of reviews I ended up wasting 50 pounds.." You grumble begrudgingly as you load it up.
Really, you were supposed to spend today doing something productive as requested by your father, but, if he's at work, how would he know what you're up to? 
"Undertale...? Sounds lame already.. Nobody's played pixel games for years." 
The music began to play, and you quickly began to read the dialogue. It explained the history between humans and monsters, and how the monsters have been locked underground for a very long time. Not long after this, your character was spawned on a bed of flowers, and you quickly made your way to the exit only to come across a yellow flower with a face.
"Hahaha what the hell? What is that?" You giggled at its humourous appearance. 
"Howdy! I'm Flowey! Flowey the flower! You must be new to the underground, aren't cha? Golly, you must be so confused! Someone-"
You couldn't keep up with his dialogue as you were too busy taking the piss out of his stupid name. You couldn't help but laugh, and you swore you saw Flowey's sprite face change to an annoyed one for a moment before returning to normal. Weird.
"See those white pellets? These are 'friendliness pellets'! Go on, collect as many as you can!" He winks and sends them towards the floating red heart that was currently in a box. Panicking for a second, not really knowing what was going on, you moved the heart sprite out the way of the friendliness pellets, causing Flowey to get quite annoyed.
"Hey Buddy, you missed them." He was about to continue, but a fireball hit him and knocked him off screen. A goat lady moved on screen.
You could tell that this was going to be one hell of an experience.

A few hours later, you found yourself wound up in Judgement Hall. The golden light and large pillars made it look almost holy like. You moved your character foward, causing it to stop as new dialogue appeared on the screen from none other than Sans.
"So, you finally made it..."
Somehow, through sheer determination, you made a point not to kill anyone. You didn't know why you didn't, you just didn't enjoy the feeling of taking that life away from someone. You had made new connections with lots of people so far in this game, and it made you extremely happy. So you were quite nervous to hear what Sans had to say about you; especially considering he was your favourite of everyone.
"Do you know what EXP is? It's an acronym. It stands for Execution Points. LOVE, is also an acronym. It stands for Level Of Violence. The more you kill, the easier it is to distance yourself. The more you distance yourself, the easier it is to not feel.."
There was a long pause before his sprite face appeared in the dialogue box like it usually does.
"But, you never did any of that. Sure, it doesn't make you completely innocent, just that you held a certain tenderness in your heart. You never gained LOVE, but you gained love. Does that make sense? Probably not..."
His speech was unlike anything else he had ever said in the game. It gave you chills, in a good way.
"Ahead of you lies the fate of humans and monsters. What you decide to do next is entirely in your hands. No one can blame you."
Before anything else, the screen goes black. There was nothing for a moment, only his dialogue.
"Somethjng terrible is going to happen soon. And you won't understand it yet. But your actions will decide your fate."
And without warning, everything went back to normal. The corridor was there, the music was back. The only difference was Sans not being there. You take a long sigh, save your game, then close it. Stretching, you stand up only to hear your dad return. You flinch, and hurriedly lock your door.
"Guess I'm not going out today.." you grumbled out, moving to your window ledge. Opening up the window, you swing your legs out, allowing the breeze to hit you as you sit there. Looking down, it was a long drop considering your house was on a bit of a hill. There were hills everywhere, really. With lovely oak trees adorning them. It was beautiful. But by far, your favourite was the huge mountain in the distance. From how far away you were, it looked like it was speckled in gold dust. However, it was only some golden buttercups.
"Wait...." pausing, you stare at it for a while, "that looks like Mount Ebott..?"
"Y/N!! WHERE THE HELL ARE YOU?!"
You startle, feeling yourself slip from the window. Looking, you watch as you fall, the ground getting closer and closer, the rocks at the bottom of the drop getting larger. Was this it? Were you really going to die?
A small black hole started opening up, getting bigger and bigger. Before you could hit the floor, you went straight through this hole, now falling into an endless void. It closed above you, blocking out all light. It was pitch black.
"HELP! PLEASE, ANYONE!??!" You screamed out, tears flooding down your face; scared for your life. You had no idea what was happening to you or what was going to become of you.
Suddenly, it felt like you're laying down on something soft. Almost like a blanket. It was warm, and you could feel a lovely light on your face. Looking up, you saw the opening of a mountain far above you. Confused, your hands brushed against what felt like petals. You look beneath you and realised you were on golden buttercups. It wasn't a blanket. You weren't even sure how you were still alive right now.
Standing up, brushing off the dirt that covered you, you started walking to a purple archway. This was all too familiar...
You saw a golden flower... with a face.....
"Flowey..?" You whispered under your breath, feeling your body freeze. You never saw the ending to Undertale, but you knew he was up to no good just by the way he tricked you at the start of the game.
He turned his head, looking mightily pissed off.
"Look, Frisk, Chara, WHATEVER! It's not fun anymore! You've messed up Sans. He knows what's going on. You can't ever win, it's just this same cycle and-" he paused as he locked eyes with you, a mixture of confusion and almost fear on his face.
"Who are you? How did you get here? What happened to Frisk and Chara?"
You seemed quite puzzled by the names, which allowed Flowey to realise that you have no involvement in any of this.
"Wait.. you don't know what's going on? Dammit, you need to leave! Somehow get out of here! It's not safe, it will never be safe. Not after those two messed it up.."
It was almost like Flowey was this completely different person. This was not the same monster who was hellbent on killing you at the beginning of the game.
"What happened here..?" You mumbled out, getting closer which caused Flowey to instinctively pull back away from you.
He didnt say anything. He just sighed, and hid underground. You stared at where he once was. What was going on? 
Plucking up your courage, you enter the ruins, only to find dust pretty much everywhere. There were clumps of it in corners or just laced across the floor, and it looked strangely fresh. Like it hadn't been there long. You felt a chill go down your spine as you continued traversing through the ruins. You found a toy knife with a rounded edge. It wasn't much, and definitely couldn't hurt anyone, but at least you could use it to defend yourself if it ever came down to it. 
After 10 minutes of walking around, you stumble across Toriel's house. The lights were on and the smell of pie emanated from the kitchen. It was a lovely homey feeling. The fire was on and faint music from a gramophone was playing. You smiled and allowed yourself to go down the stairs where you knew the door to Snowdin Forest was. It was only a few minutes, but before you turned the corner, you heard two voices. An older ladies voice, and a young mans voice.
"P-please! I'm sorry if I d-did anything to anger you sir! But p-p-please don't h-hurt me!" 
"Sorry Tori, but I gotta be prepared for when the human starts another shitty genocide."
And without warning, the sound of something summoning could be heard followed shortly by something being stabbed and a scream. Something could be heard turning to dust, and then there was silence. You peer your head round. Nothing was there other than a significantly large pile of dust. 
"What.. what the fuck just happened..?" You could feel your heart rate increase as a wave of sorrow washed over you. You just heard a monster get killed and you did nothing to try and stop it.
You stepped forward, realisation crossing your mind. That was probably Toriel. This caused overwhelming grief to take hold as you knelt besides the dust pile. Tears rushed to your eyes as your favourite goat mom was now dead. She wasn't ever coming back and there was nothing you could do about it. And that thought killed you.
However, there were more pressing matters at hand. Someone was on a murder spree and you had to stop them before more monsters were killed in a bloodthirsty massacre. And more importantly, who the mystery monster killer was.
You hurriedly opened the doors and rushed out, your feet sinking into the deep snow. Funnily enough  there were zero footprints around, which means no one has been here for a long while. The forest was quite dark, and an awful chill lingered in the air. This wasn't the Snowdin Forest you remembered...
"Hello? Is anyone here?" You called out, hearing your soft voice echoing back to you. 
Taking a deep breath, you decided to press on, running straight through the gate that was too wide to stop anyone. However, your hope for monsters still being alive turned into dread as you began seeing piles of dust next to everything. Trees, rocks, clumps of ice, sentry stations: Everything. Whoever it was killing them, they didn't waste any time and were extremely quick about it. You doubted there was anything you could do, but you still had to try. 

It didn't take long for you to stumble across Snowdin. It was a complete ghost town. All life had completely disappeared. Even Grillby's, known for its jovial and loud nature, was silent. Not a soul in sight. 
"Wait a minute... is Sans and Papyrus alright?!" 
You wasted no time running to the skeleton brothers house, barging through the door and inspecting the surroundings. Funnily enough, the place looked pretty much how you would expect. And it seemed like it had been used recently too, which was always a good sign. The only odd thing was the small trail of dust that led to Sans' room. However, you didn't bother trying to check his room as you knew that even from the game, it was always locked. So, feeling quite defeated, you leave the house and start taking the path that lead to Waterfall, only to completely freeze in a mix of pure horror and confusion. 
In front of you stood Sans, his hood up and completely covered in dust. In front of him was Papyrus, bones behind him so that he couldn't run away. 
"P-PLEASE SANS, I'M NOT SURE WHAT'S GOTTEN INTO YOU, BUT W-WE CAN W-WORK THIS OUT!" Papyrus tried negotiating, only for it to fall on death ears.
Sans let out a low chuckle, as if he had heard his brothers speech all before. As if it was amusing. He shakes his head slightly.
"Come on bro.. I can't let the human kill you.... I'm doing this out of mercy... I can't keep watching them kill you over and over and over-" he kept repeating himself, trailing off and growing quieter, causing his poor brother to flinch and take a small step back.
"Can't you see Papyrus? I need to have more EXP than them.. to have more LOVE than them so I can finally put an end to this stupid cycle.. " he growls out, venom laced in his voice, as if the very thought of whoever he was talking about made him sick.
"IF THAT'S TRULY WHAT YOU BELIEVE, THAN.. I.. THE GREAT PAPYRUS WILL HELP IN ANY WAY.." Even though he was trying to sound confident and even though he was trying to reassure his insane brother, you could still hear the doubt and fear hidden in Papyrus' words.
"Good.." And so without warning, Sans summoned at least 8 bones that went straight through Papyrus' body, dusting him almost immediately, causing his armour and red scarf to lay neatly in his pile of dust. Sans walks over and picks up the scarf, gently putting it on himself as he silently mourns the loss of his favourite monster.
You couldn't help but let out a small gasp, a sound loud enough that made the skeleton snap his head towards you instinctively. A horrific grin crept onto his face.
"Well well well.."
He disappeared; in a moments notice re-appearing behind you, tightly gripping your neck in such a way that hurt terribly but still allowed you to just about breath. You stared into his eye sockets, taking note of his mismatched pinpricks. One being fully red while the other was red with a blue ring around it. You also couldn't help but notice the sheer amount of dust that caked his body and clothes, which also fell off of him like snow with every small movement he made. Sans' pinpricks glared into your own eyes, as if trying to find out whatever hidden intentions you may hold.

"What do we have here?~"