Sans AU One-Shots

Error 404 || file malfunction.

Pairing: Error!404 Sans x Female Reader
Prompt: Due to an unfortunate mistake, Y/n finds herself in the mainframe, and she barely manages to survive the ensuring attack from a very confused Error 404 before he decides to use her for his benefit. But since he has an aversion to talking, she can't get a read on him, and it's impossible to tell what he'll do next - or when he'll decide to finish what he started that first day.
Type: high tension, talking to a brick wall would provide a better conversation, I'm doing my best with what I've got, mysterious 404
Length: 6k words
Background: I know next to nothing about Error 404, his lore especially. I tried to do research into him, and here's what I found: 404 is in the mainframe - an offshoot of the anti-void - where he likes to be alone and talk to himself as he fixes 'problems'. He's manipulative, always in control of any situation, domineering, and acts like a sociopath (as if his god complex wasn't enough). 404 believes the ends always justify the means, and bro is overpowered af (you can't even kill this mofo cuz he'll just regenerate in the mainframe). His abilities include: taking control of people's souls where he can mess with their mind and influence them, telekinesis using blue magic, all of Superman's gifts (speed, strength, etc) without his kryptonite (like I said, OP af), and bro can fuse with characters like Error cuz why not. He used to be in a relationship with Chara but has since sworn off love because he lost her, and he treats Error as a prodigy and the two work together often.
You're a Chara from an unnamed AU and you hang out with the monsters of the underground peacefully, growing up under the loving goat parents with Asriel since you never died (unlike Undertale Chara). You did however have the ability to reset, and unbeknownst to the others, you used that to try out more than just a pacificist run.
Notes: Requested by the lovely yourl0calw3irdo_z. | If anyone could find me a concise read-up on his lore, that'd be much appreciated cuz I'm not reading 300k words worth of content to learn about 1 character. Also if 404 seems OOC to you, I do apologize - I'm working with what I've got.

~-~-~-~

(Y/n) blinked slowly, the chocolate chip cookie she'd partially risen to her mouth falling back to her side as she stared up at what appeared to be different AUs among scattered drawings, with the focal point of some of the scenes being specific people like the cameraman was tuned into whatever they were doing at any given moment. She blinked again, sure she had to be imagining things because last she checked, she was messing around with her AU's files while chowing down on cookies, not in some endless white space. Her AU looked nothing like this place – actually, she doubted any AU had such an affinity for white nothingness, so where was she?

She turned in a slow circle, spotting a white and blue figure a half-second before she dove to the side, narrowly missing a blast right where she was standing. Adrenaline shot through her veins as she put her hands up, still clinging to the cookie as she shouted for the stranger to stop. Either they didn't feel like listening or didn't care, because the next second, a ray of light shot through her, paralyzing her to the spot. Her mouth was still open in her attempt to explain herself, and she watched with horrified eyes as the person came closer. His darkened fingers were still pointed at her, prepared to unleash a Gaster Blaster level blast at her should she even twitch, and she was powerless to do anything.

"How did a human get in here?" he mumbled to himself, the smallest flicker of confusion passing over his poker face. He reminded her of Sans, though there were blue streaks down his cheeks like he was permanently crying and she couldn't recall Sans ever being able to fire a Gaster Blaster blast out of his fingers instead of the skulls she was used to – she'd fought him enough times to know. The stranger's attention drifted to the cookie still clutched in her hand, and after a moment of thought, he snatched it from her, knocking her arm to the side in the process, and suddenly she could move again.