Experiments:Yandere!Assorted Characters x Reader

Chapter 1: Helping Alphys

"(Y-Y/N), just sit s-still, please," Alphys begs, giving her subject an exasperated look.

You give a small sigh and attempt to stop wriggling; you'd never been the best at sitting still. As you wait for the experiment to commence, you turn your thoughts to the purpose of the test. Alphys wanted to test the emotional connection that one feels when they see another, and how they differed between monsters. You could understand that. What you didn't get is why you, of all people - monsters, whatever - had to be the one testing the bonds. Sans, Papyrus, Undyne, Mettaton, Toriel, Asgore, and Frisk all sat a few feet away, sitting on stools and chatting about this and that. You hated being watched, put so close under a telescope and having your flaws on display.

"(y/n). (y/n). (y/n)." You hadn't even realized Sans was now standing beside you, poking your warm cheek with each repetition of your name. You focus on him, raising a brow in silent wait for his response. "entertain me."

You huff and give the skeleton a light shove, turning your eyes back to Alphys. "Almost done there, chief?"

Alphys stares at the computer for a few seconds before nodding, facing the group. "I-if everyone could t-take their seats, we c-c-can get this done real fast. P-probably." Sans saunters back to his stool while you sit straighter, trying to quell the itch of fear in your mind. Alphys removes her glasses for a moment, cleaning them on the edge of her sleeve. It was clear she was nervous, more so than usual - the brain was a very delicate thing, after all. "N-now, I'm going to t-try to manipulate everyone's emotions a little bit, see h-how the amalgam reacts u-under different chemical i-influences; these ch-chemicals being the emotions you a-all feel." Alphys hadn't said anything about changing the emotions, and Undyne opens her mouth to say this. Upon seeing just how nervous her girlfriend was, however, she falls silent. Alphys steps back to the console, pulling a lever to create a glass divider between her subjects and her test object. "Th-this is just in case you guys f-feel violent; (Y/N) doesn't h-have powers, so she c-couldn't defend herself v-very well. I'd h-hate to see her get hurt, much less k-killed." You have a feeling it was also so that if things did turn into a fight, Alphy's machine wouldn't be harmed. That was secondary, you suppose, but it was probably true just the same.

Each monster has been hooked up to a separate monitor, displaying their heart rate, brain activity, and a few other things you don't bother focusing on. A few wires are connected directly to the everyone's temples; they would administer the shocks that changed the monster's - and Frisk's - mood, Alphys explains. You had always thought manipulating the brain was more difficult than that, that it required cracking open the skull, but who are you to judge? With a nod to the others, Alphys twists several knobs and flips two switches.

The effect isn't immediately obvious. Everyone holds a steady gaze, some smiling, other's neutral. As you watch, Undyne's expression twitches from a wide smile to a slight frown. Frisk's leveled face lowers slightly, and Mettaton looks disgusted. Sans was grinning, but his eye flashes blue every few seconds. Toriel glares at you with hard, unkind eyes, and Asgore bares his teeth. Papyrus is the only one who looked unchanged, happily waving to his dear friend. You hear Alphys mutter under her breath, writing things down in her notebook.

It's getting harder to sit still, to look at the faces that were growing even angrier. "A-Alphys," you ask, not letting your eyes leave the group and a small squeak as your voice, "Can we be done with this part of the experiment now?" You tremble and grip your seat, hard. You turn to fully look at Alphys, who was now looking. . . Looking behind you?

You slowly turn, nearly falling out of your seat. Undyne has her face pressed against the glass, Tori and Asgore a few steps behind. Mettaton is still on his stool, and Sans is balancing on the edge of his, both uncertain of whether or not to stand. Frisk is crouching on their stool, eyes narrowed in anger. Papyrus is looking around, confused. "Interesting," Alphys mutters, "Papyrus has such faith in you, no matter what false memories I create to change that, he's still optimistic. . . now that's determination. . ."