Under all (AU Sans X AU Reader)

~Open to Fell~

Another reset
You laid in the patch of flowers, frisk trying to get you up.
"No Frisk... I just want to lay here a moment..." She pulls your arm and you just go limp. "I will catch up later ok?" She eventually sighs and gives up, running off to find Toriel.
You just lay there, you knew you couldn't sit here until the reset, you had to move on. You just wanted to wait long enough to be able to avoid Sans. Maybe he will come around with time... but... he did break up with you.
You sigh, finally get up after about half an hour and head towards the ruins.
However where Flowey should be there is something else. You weren't sure what it was. It looked like a hole through a wall... minus the wall. It was just floating in air and the area beyond it was white.
You were a bit worried, no matter how many timelines you wound up going through you had never seen something like this. However your curiosity was more prominent than your fear and decided to try and touch it.
You edge forward and stick your hand through to the other side.
Nothing.
So you pull your hand back and this time stick your head through.
It was kinda just an empty white space with white walls and an endless seeming ceiling.
Your footsteps echoed through the room as soon as you step through the portal.
You take a few steps forward and then you feel a hand on your shoulder.
"YoU sHoUlDn'T bE hErE (y/N)" They made you jump and the odd voice sent a shiver down your spine. The voice jittered and faded in and out like they were broken.
You turned to see a person that almost looked like you except her clothes were deep white and almost faded into the background making the other parts of her body that was showing almost look as though they are detached. She looked so pixelated and had the word "Glitch" painted all over her body.
Seeing her made you fall backwards in shock and a little fear. A laugh echoed around the room from her, vibrating off the walls.
"Who are you? H-How do you know who I am?"
She extended her hand to help you up. "I aM yOu, A vErSiOn Of YoU tRaPpEd In ThE wAlLs BeTwEeN tImElInEs... DiD sAnS eVeR tElL yOu AbOuT hIs ErRoR sElF" You nervously accept her gesture and let her help you up. You nod in answer to her question. "WeLl I'm ThE eRrOr VeRsIoN oF yOu, I gO bY gLiTcH"
"Well nice to see you I guess" you give a nervous smile. You have heard very little as Sans wouldn't explain anything about Error. All you knew was of him and that there were other versions of the underground. 
"I hAvE sEeN tHaT yOu ArE hAvInG sOmE tRoUbLeS?"
You give a sigh "Yeah..."
"DoN't WoRrY. yOu ArE nOt ThE oNlY yOu WhO hAs TrOuBlEs GeTtInG aLoNg WiTh YoUr CoRrEsPoNdInG sAnS" She looked a little lost in thought and started to pace back and forth. "I CoUlD gEt In So MuCh TrOuBlE wItH eRrOr... WhY dO i CaRe? I aM aLwAyS iN tRoUbLe WiTh HiM... hOw WoUlD yOu LiKe To Go On A vAcAtIoN?"
"What do you mean?"
"In AnOtHeR tImElInE yOu... WeLl... YoU aRe KiNd Of A dIcK... AnYwAyS wOuLd YoU lIkE tO vIsIt ThErE aNd SeE tHe UnDeRfElL vErSiOn Of SaNs?"
You didn't want to go back, you couldn't deal with how your Sans became so cold. You were lovers before all this and he broke up with you because of something out of your control. It was time to get away for a bit.
You gave a short nod to your glitch self and she responds with a smile. "AwEsOmE!" She steps away and opens a portal that has a red glow.
"ThIs Is UnDeRfElL.... I aM pUtTiNg YoU rIgHt In SnOwDiN sO wE cAn aVoId ThE fElL vErSiOn Of yOu... NoT gOnNa LiE sAnS wIlL cAuSe tRoUbLe HeRe... GoOd LuCk AnD tRy To AvOiD yOuRsElF!" and with that you were pushed through the portal into a whole new version of your own world. 

~

You kinda hid seeing as everyone was angrier, colder and much more violent. It took a lot more effort to spare the few monsters that spotted you and mostly you had to just run away.
You decided to just go and look for Sans and Since you were already in Snowdin the first place you would try is Grillbys. Same as back home the vast majority of monsters have never seen a human so they thought you were just a different looking monster. You really wouldn't be able to tell though as you were met with hostile glares the instant you entered the building.
The air in the building tasted of smoke and sulfur, the few monsters that were there had a scowl on their face as you looked to the counter in a position where your Sans usually sits there was a monster with his back turned from you dressed in red and Grilby himself was made of a dark purple flame instead of his usual orange color. He almost seemed to suck light in rather than put it out.
You let the door close behind you and headed up to the counter and set next to the monster. He took a glance and did a double take.
"Well Well (Y/N)! You are early." It was almost hard to recognize him, even when you saw his face since he had jagged teeth and one gold tooth and his most prominent color was red instead of the usual soft blue. Somehow though you just new it was Sans. "Shall we go get our usual 'Chat' over with sweetheart?" For some reason the way he said "chat" made you nervous.
"But I'm not..." you didn't get to finish before he put his arm around you and suddenly found yourself on the outskirts of Snowdin with Sans face in front of yours.
Startled you fall back and somehow accidently dodge an array of bones popping up right where your head was.
"S-Shit..." You were breathing heavy and Sans laughed.
"Come on (Y/N)! Where is your usual attitude?" You saw a red glow in his eye and he shot a few bones at you and you wound up rolling out of the way.
"And where is your knife? Don't tell me you lost it sweetheart" He laughed and your soul glowed blue and he thrust you against a tree, you gasped as the wind was knocked from your lungs.
"And what's with the new getup? I didn't think blue was your color..." He walked up to you again and was right up to your nose.
You try to regain your breath and speak
"I'm not... your... (Y/N)"
He gives you a confused look but doesn't let you down. "What do you mean sweetheart? You look the same as ever apart from the clothes"
"I'm from a different timeline."
"Heh and i'm supposed to just believe that? Trying to trick me and then mock me next timeline again?" He gave a shrug and a smirk "not going to fall for it again." He snapped his finger and bones floated around you.
"W-wait! how can I prove it?" You struggled to free yourself from the tree and he smirked.
"You would have to do something she would never do."
From what you knew she was violent and even killed Sans so showing some form of compassion would be a way.  
You had one idea come to mind... and you were not going to lie you liked the idea but...
well Sans did leave me.
You managed to pull your arms free and grab Sans by his red sweater.
"What are yo-"
You put your lips right on his teeth, kissing him deeply.  

~All~

"So you kissed the red bastard" (Fell/y) laughed
(Patch/y) gave a chuckle as well "I bet thats not all she did with him." 
Classic's cheeks flushed red "Y-yeah..."
Fell laughed even harder. "You fucked the red devil? Man talk about desperate!"
"Actually..." Classic looked down and twiddles her fingers looking as flustered as ever. "He was really hot... kinky as fucking hell..." 
"Well..." (After/y) started, looking at you while laying on her side "You don't get to spare the details now that you mentioned that." 
"YoU sHoUlD cOvEr YoUr EaRs FoR tHiS oNe SwAp" Glitch gave a vibrating laugh before (Classic/y) started to give some of the details of her sinful night.

~

(If you cant guess next chapter will have a lemon, this book will have a lot of them i can assure you.)