(Underfell sans x reader (female)) UNDERCOVER

He's just...

          This was unreal―you never thought you would be invited to such a big event, maybe even one of the biggest events in the Underground. The closest time you could think of yourself being at 'party' is when you treated yourself to the leftovers in the fridge on one of your birthdays. Feeling nervous and anxious about the ball, you ask Papyrus further details.

"Um, Papyrus? When exactly is this ball going to be?" I ask.

"WHY TOMORROW OF COURSE!"

          Your heart dropped a thousand miles down in your chest with dread. You did like the idea of going to this ball but the fact that there are going to be a bunch of monsters in the same place made you fear for your safety of getting caught. It also didn't help that one of the monsters that's going to be there that Toriel warned you about was King Asgore. The thought of your mask slipping off your face and revealing yourself to every monster including King Asgore was causing you to hold your breath without even knowing. You let out a big breath of air which confused Sans.

"you alright there doll? you seem a little too on edge." Sans says concerned.

"I'm fine, I just got lost in thought." I tell Sans.

"hmm...somethn' tells me that's not the case."

          Sans always seemed to know how you really feel, either he's very observant or you are just very obvious. You sigh knowing that you have no choice but to tell him what's really going on with you.

"come on, what is it~" He teases.

"Alright fine. I think it's a bad idea that I should go to the ball because i'm worried I might get caught―and I don't know what i'm going to wear."

"DON'T WORRY ABOUT THE OUTFIT DETAILS (Y/N)! METTATON IS COMING OVER TO EVERY ROYAL GUARD'S HOUSE TONIGHT AND IS TAKING THEIR MEASUREMENTS SO WE CAN FIT INTO OUR NEW UNIFORMS HE'S MAKING!" Papyrus says excited.

          Something didn't add up in that sentence that Papyrus just said and that started to make you nervous.

"Wait, could you repeat what you just said Papyrus?" I ask him.

"DON'T WORRY ABOUT THE OUTFIT DETAILS?" He says confused.

"No the other part."

"METTATON IS COMING OVER TO EVERY ROYAL GUARD'S HOUSE TONI―"

Papyrus immediately realized what he had just said and literally jumped off the couch.

"OH MY GOD I'M STILL IN MY BATHROBE AND YOU'RE NOT IN DISGUISE!!! (Y/N)! QUICKLY GO AND GET DRESSED, METTATON COULD COME BY ANY SECOND! I CAN'T BELIEVE I FORGOT ABOUT THIS!!"

          You quickly rush to your room remembering how you felt when Undyne was very close to finding you when you were hiding in the kitchen closet. You lock your door and change into your disguise as you hear Gaster writing on the chalk board. 

[I have heard a lot of noise in the past few hours and I demand an explanation.] Gaster writes.

          You skim through Gaster's response before adjusting your mask and hood on and try to tell him what happened while talking through your voice changer part of your mask.

"I was having fun with Sans when all of a sudden Papyrus burst through the front door, picked me up, and threw me into the kitchen closet. Long story short, Undyne came to teach Papyrus' at cooking lessons and almost found out where I was hiding without even knowing...She also destroyed the kitchen as a result of her poor cooking abilities."

You take in a deep breath from your mouth-full reply as you wait for Gaster to respond.

[I cannot believe you almost jeopardized your entire life just because you were having 'fun' with Sans!]