Under the mean face(Underfell Sans x reader)[COMPLETED]

(I don't have a title)

Sans?! What... and there's the skeleton I've seen during the time I was an experiment. What? Does that mean....

Sans- Hey sweetheart, did ya found anything?

You- U-um, no... Nothing important.

Sans- Are ya trying ta lie, 'cause you're really bad. Give me that document.

You- N-no!

Sans- What is so terrible that need to be hide? Let me seeeeee!

He childishly pleaded me, but this was serious. Bring back such bad memories to him wouldn't do any good. I raised my hand out if his reach, but a red aura enveloped the document and took it out of my hand. He looked at it smirking at my, but his face went blank when he saw it. He seemed really shook and his eye sockets were now black empty holes.

Sans- ... Did you red it all?

You- U-um, maby?

Sans- Shit... I.... I-I didn't want ya to.... Aah, fuck! I-I need to do something.

He shoved me out of his way roughly and left the room. I stared at the doorway, hoping that he'll come back soon. After a few seconds, I turned around and sat down on an old dusty chair that creaked under my weight. I let myself being flowed in thoughts. Why did he reacted this way? What am I gonna do about the soul thing? How can I see the other skeleton? Do I need to remove a fragment of my soul? How am I gonna do that with Sans? Deep in my thoughts, I didn't noticed the growl that came from the corridor out of the room. I got out of my thoughts when a loud bang shook the door. I yelped in fear as the banging sound continued until the door flung open. In the doorway was standing the doggo amalgamate that Alphys created. It was barking and growling loudly at me. I fell from my chair and crawled back until my back hit the wall. The creature squeezed itself through the door and walked slowly toward me, growling. I searched for something useful, then I saw an old broken pipe. I took it and putted it in front if me as a weapon. The dog stopped and sniffed the air, then it started to bark excitedly. I stared in confusion, but soon understood when I realized that it was still a dog. I shook the metal pipe in front of it's hole/face(I don't know what to call it) and it started to bark. I thrown the pipe beside me so I could pass beside him to get out. I ran into the corridor and closed the door. I ran further away from the amalgamate and once I considered myself far enough, I called out for Sans. As I walked deeper into the dark creepy lab, the air seemed to grow heavier and more tensed. I passed in front of the place where Alphys cut my first finger. It was really painful. I unconsciously touched my hand with three missing finger from the tip of my fingers. I grew more stressed as I saw the old cells with blood stains and dirty beds. I shivered and my heartbeat fasten along with my breathing. The horrible memories flooded through my mind, making me cry. I rested my back on a wall, trying to calm down, but the memories of the slices and cuts made by the bloody scalpel invade my brain. I let myself slide down the wall, crying and hyperventilating, I grabbed my hair and pulled them, trying to make the pain stronger then the memories. I just wanted to think about other things! I bite my arm until I felt a warm liquid dripping down my arm. I tried hard to stop crying and calm my breathing, but I couldn't. I clawed my back and bite my arm, I screamed and let out the fear, but it didn't help. I was having a huge panic attack, and nobody was there to help me. I screamed again and again, having a hard time to breath and slowly, I was lacking air. I stayed on the ground trying to calm myself until I heard running footsteps coming towards my direction. I didn't looked up and continued to claw myself, cutting my skin as blood was pouring down from my wounds. I felt a pair of arms grabbing my wrists and pulling them away from me. I cried even more, thinking it was Alphys again. Suddenly, something wrapped itself around me and no longer around my wrists, I struggled a bit, but words echoed my mind.

Sans- Shhhhh, calm down. Focus on my words. Breath in and out..   in and out....

My breathing slowed a bit and I did as he said. I soon relaxed and hugged him back. Burrying my face into his neck, crying softly. He stayed like that and gently rubbed my back, calming me faster. I was back to my normal mind state and Sans was holding me close to him.

Sans- Are... Are ya okay?

You- Sorry. I'm so sorry, I didn't wanted to worry you! I'm so, so sorry!

Sans- Ya don't need to be sorry, I should be the one apologizing right now. I left you alone. Sorry sweetheart. It's okay now, I'm here.

You- T-Thanks Sans.

I hugged him tightly and he pulled away to kiss me deeply. I melted into the kiss, my fears slowly fading away. I pulled away and stood up, hissing in pain from the wounds on my back.

Sans- We should fixe that.

You- Yeah...

He leaded me to a room where numerous medical kit and devices were exposed on many shelves. He took out bandages, alcohol and a towel. I poured water on the towel and came toward me.

Sans- Ya need to remove your shirt.

You- Wha-

Sans- Remove your shirt or I'll not be able to fixe your wounds.

I sighed and blushed a bit as I removed my shirt. He stared at me then blushed madly before walking behind me. I hissed at the contact if the wet towel. He carefully cleaned the dry blood off and  used a sponge to pat gently the wounds with alcohol. I hissed once again, but bite my tongue to stop. He wrapped the bandages around my back and shoulders to keep them in place then I place my shirt back on. He then did the same for the biting marks on my arms. 
He finally finished and placed back the things to their places.

Sans- Hey umm, (y/n). I... I think need ta explain ya a couple o' things.