Undertale AU Sibling Oneshots

Overprotective! Fell! Alphys x Shy! Caring! Short! Sister! Reader

(me for the past week: Me: I wanna write My Brain: how bout NO)
(holy cow that title's a mouthful, anyway hope you like this one)

Requested by the lovely kittylove32!~

You were still a child when you fell underground, running from various monsters as you traveled through. You eventually came upon Alphys' family, and upon seeing you, they were gracious enough to take you in and keep you safe.
You grew up in the Underground, known throughout as Alphys' little sister.
One day, another human fell, and this one managed to free all of the monsters. That's where you were now, helping your sister move her things up to the surface. You, her, and Mettaton all got a house together, but you were sure Alphys would end up living with Undyne anyway soon.
She always made sure you weren't pushing yourself, telling you to leave the heavier things to Mettaton or Undyne. You would always brush off the behavior, just simply used to her overprotectiveness. Even still, you let the others do the heavy lifting.
Once you were settled into your new home, you and everyone else would take turns preparing dinner for the whole gang at one house.
It began as a one-time only thing, a little celebration towards making it to the surface, but it soon grew into a weekly thing.
And over time, you slowly grew closer to Sans, the walls your shyness built slowly broke down around him. And all the while, you were blissfully unaware of Alphys glaring daggers into him every time.
You even dared say you had a crush on him.

It was when you and Alphys were in her room, talking about nonsense as usual. You had mentioned Sans at one point, just something nice he did for you the other day.
"Don't fall for it, (Y/n)! Boys are nothing but cruel and gross!" Alphys hissed, gaining that protective look on her face that you knew all too well.
"Excuse you!" Mettaton gasped, walking past the doorway, looking only slightly offended.
You snickered and shook your head, smiling a bit to yourself. If you didn't know your sister was a diehard lesbian, you would've thought she'd had a horrible boyfriend in the past.
"Alphys, I can take care of myself."
"I know! I-It's just—!"
"Are you worried about me?" You asked softly, tilting your head with a small smile.
"I just don't want you getting hurt. We almost lost you when you were little."
"I know, Alphy. But you really don't have anything to worry about. Sans may be strong, yes, but he thought he killed me one day after lightly smacking me in the forehead with a cabinet door."
Alphys snorted, hiding the sound and her grin behind her hands.
"Besides, if he does screw up, you get first dibs."
"I'm holding you to that!"
"I know, I know! Now, we need to watch that anime I mentioned the other day!"
"Isn't it the one where the guy eats some old demon's fingers to gain power?"
"I—sigh, yes, but there's more to it!"

(Let's play guess the anime! First person to guess which anime I meant gets a shout-out next chap!~)