Sans AU One-Shots

Classic || backrooms.

Pairing: Undertale Sans x Female Reader
Prompt: We made it to the end, we're at the barrier, but instead of all 6 human souls waiting for us, we're 1 short. Which means 1 of us has to kill another to take their soul, combine it with the 5 waiting souls, and break the barrier for good, because only a single being harnessing the power of 7 human souls has the strength to break the curse placed on the monsters. I'm nominated as the killer because I have the most determination, but looking at the 3 friends that accompanied me throughout the Underground, how can I bring myself to kill any of them?
Type: mystery/reveal, ADHD brain on crack cocaine, real people in fictional world, Sans is hiding something...
Length: 9.3k words
Background: This was a joke idea between some friends of mine inspired by the thought 'what if we fell into the backrooms, but instead of the backrooms, it was Undertale?', and from there, I predictably got ideas and wrote a thing (or multiple). It's going to be a series so heads up. | You enter the backrooms by being in the wrong place at the wrong time and 'clipping through reality', so-to-speak. How fortunate we would end up somewhere we actually want to be instead...
Notes: So, fair warning, my ADHD brain is on full display in this one-shot thus the conversation bounces between topics despite Sans' ability to rein Y/n in and keep her on a leash (you have Blue to thank for that comparison lmao). It's also a different format than my others, as you're not in the midst of the action, but hopefully there's enough mysteries and reveals and drama to keep you entertained 🤭🫶

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I watched my friends disappear at the end of the last corridor before the throne room - before the end of our journey through the Underground and Undertale's storyline - and I came to a halt as their shadows rounded the corner out of sight. For a long moment, I stood there, my back to the barrier we just walked away from and a lot more on my mind than when we all first entered. As if knowing he'd be there, I glanced to my left to see Sans the skeleton leaned back against one of the many pillars lining the corridor, his sockets closed as if asleep, but I knew he wasn't.

My friends were silent as they left, even their footsteps failing to echo their way back to me, so I waited with Sans until his sockets slid open to signal we were well and truly alone. "You lost, kiddo?" His deep voice wasn't loud, but in the stillness of the room, it bounced off the walls and disturbed the dust in the air, causing it to dance in the pale orange light streaming in through the stained glass windows.

"Yeah, I need directions to the hot single skeletons in my area?" I tried to smile at him, but it was forced and unnatural on my lips. He could tell.

But he played along, glancing back and forth before shaking his head regretfully. "Sorry, kiddo, you just missed 'em. Guess that leaves me." He held out a hand, already knowing what I wanted somehow, but I didn't question it. He's always known far more than he ever let on, and I wouldn't be surprised if he heard every word of my friends and I screaming at each other at the barrier.

"You're a hot single," I disagreed as I took his hand, earning a low chuckle in response as he raised a browbone at me to ask a question without putting in the effort to form the words. "Yes, the 'skeleton' bit is the part you lose me on." I shook my head with mock disappointment, fighting back a smile, and I almost missed the surprise on his face.

"You learn me better and better each day," he murmured, and keeping his grip on my hand tight, he teleported us both back to Snowdin. We faced Grillby's, and he was already reaching for the door as I gave his back a confused look.

"I thought we established I'm a cringey fangirl of yours, I have to commit to the bit." It was a self-deprecating joke, one he chuckled at while simultaneously rolling his eyelights, and he pushed the door open with his back so he could look at me.