(Underfell sans x reader (female)) UNDERCOVER

Overlooking a few details

          You were at the door with the key in your hand, you were ready to see what was hiding in the basement that Sans kept locked. You put the sliver key into the key hole, hearing a click that meant it has been unlocked.

          The door opens but you couldn't see much but a dark stairway with a light bulb hanging down at the bottom. You could feel a slight breeze coming from the basement as you muster enough courage to to take the first step. You noticed a light switch on the wall next to you and flipped it making the light bulb at the bottom of the stairs to flicker on, illuminating just enough for you to see dust covering each steps along with cobwebs that were above you.

         You close the door and lock it from the inside, cutting you off from all sound that came from behind that door.

"This totally something you'd see out of a horror show." I say trying to comfort myself.

          You were scared even though you knew Gaster was with you but it didn't help the fact that he's basically a ghost. You take another step and hear it creak and so did the rest of them as you walked down into the dark abyss. You hadn't left the last step yet as you feel for a light switch on the wall that lead to a darker room, you feel a knob of some sort and twisted it. You hear a quiet hum as you see fluorescent lights flickering on and showing you the rest of the room.

          The place looked like a mini laboratory with a light purple tiled floor and gray-blue walls. Your steps echoed as you walk into the lab more and see something giant that's been covered with a blanket. Across from the mysterious covered object was an empty work space that is built into the wall that looked liked a place where you do experiments.

          You take out the folded pieces of paper you brought and smoothed them out on the empty work space waiting for Gaster to write anything. As you waited, you saw there were four drawers that distracted you as you try open them. All four drawers were locked except for the second one which had a freshly wrapped bandage inside that you take so you can use it if you ever get badly injured in a battle with another monster. Your curiosity now moved to the giant covered object as you walked towards it but you suddenly heard something from behind and jumped back. The papers you set on the shelf were moving and shuffling around as you hear furious writing noises. You forgot about the giant covered object and went ti see what Gaster was frantically writing about.

[It's best you don't touch anything in here without my permission.] He writes.

"And why is that?" I ask.

[First of all: this is my place, and second: there is very dangerous equipment in here, so I don't want you to get injured.]

"Technically, this is Sans' place because you supposedly don't 'exist' anymore." I say using finger quotation marks on the word 'exist'.

[What's that supposed to mean?] He questions.

"You can't entirely not exist unless absolutely no one knows who you are, including me and Sans' faint memories of you."

[Good point, (Y/N).]

There was a pause that caused you to become very puzzled. 

"Gaster? "

[Yes?] He replies.

"I can't exactly remember why we came down here." I say with a small nervous laugh.

You could tell Gaster was thinking too since nothing was happening between the two of you.

[Now that you've mention it―I can't really remember as well, which is strange because I never forget things.]