(Underfell sans x reader (female)) UNDERCOVER

Falling apart

Your heart was pounding out of your chest as you began to panic, wondering what Alphys meant by Sans having the power of deciding your fate. Sans was shaking with anger as he yelled for an explanation.

"what do you mean i'm going to be tested on the fate of (y/n)'s life!?!" Sans yells.

Alphys adjusts her glasses and smirks as she takes out a different remote from her lab coat. She presses a button and four identical switches came out of the wall. Sans looked at them confused and turned to you who was just as worried. Alphys grabs her clip board and writes down a few notes, most likely the reaction of you and Sans towards the switches.

"Each of these switches do a certain task. Do you see those two tubes on either side of (y/n), Sans?" Alphys says smugly.

He growls and nods.

"One of them is filled with water and the other is filled with Sulfuric acid. Do you know what sulfuri―"

"yes! i know what it is, what does it have to do with the test!?" Sans retorts.

Alphys' smile grows dark and mischievous.

"One switch empties the water filled tube into (y/n)'s and drowns her, and one other switch empties the sulfuric acid one and burns her alive!" Alphys says holding back her laughs.

Sans snapped and grabbed Alphys by her lab coat and slams her against the wall, putting her in a bit of a daze as she glares at Sans.

"May I remind you Sans that I have the power to kill your little girlfriend over there with the press of a button..." She says gripping a controller.

"...any violent acts during the testing will also result with this button being pressed which will drain all oxygen from her tube and suffocate her." Alphys spits back.

Sans lets her go with the look of defeat as she continues. She fixes her lab coat and clears her throat.

"So far you have 25 percent chance of saving (y/n) from the options i've given you, but that might raise to a 50 percnt by the other two options. The last two switches do the following: one of them will give (y/n) a scuba mask with a tank of oxygen and the other switch does nothing. You must choose two switches but think carefully as you may know that some combination of certain choices will result in horrific consequences."

After hearing this you realized that you have no control over this and Sans was literally holding your life in his hands. Sans however was looking just as scared as you were.

"I Thought you said killing me would be a bore, remember!?" I yell at Alphys through the glass.

"I'm a good liar aren't I?" She looks at you and chuckles.

Alphys writes down a few more things and looks at the two of you.

"I'll be watching the two of in the other room so don't try to do anything stupid Sans" She says reminding him by showing the remote again.

"Good luck, You have one hour~"

Alphys walks out of the room and locks the door behind her as a few camera that were placed around the room activated, staring at you and Sans. A timer above the four switches turns on and begins counting down from one hour. Sans runs over to you as you tried not to show him any signs of you crying, but he had already noticed and began to comfort you.

"it's okay (y/n), i'm not going to let you die in there."

But that's not what you were crying about.

"This all my fault, I should've just stayed with Flowey and Toriel in the ruins. Now i've destroyed you and your brother's lives and possibly die because of me." I sob.