Headless Brother (aka Dirty Brother Killer)

Disappointment

I raised my blade, ready to strike.
Then I noticed him; his left blue eye ablaze with anger. He stood among some of the trees in the woods a few feet away. I could almost feel his fury from where I was standing.
But my hand acted on its own and quickly sliced from left to right with the knife it held.
My soul immediately regretted the decision.
The pearly white skull fell into its owner's hands. The body promptly vanished, and the head softly landed in the snow.
"I know you can do better," it said, "I believe in you..."
And it disintegrated.
I looked to what killed my friend. My scheming hand.
I dropped the bloody blade and fell to my knees, tears streaming down my cheeks.
Then I heard light footsteps coming in my direction.
"Kid, you don't know what you just did. You'll soon come to wish you didn't do it," A deep voice warned.
I slowly looked up.
There he was. Sans: Sans the skeleton.
He wore a blue hoodie, black shorts, and fuzzy pink slippers.
Both of his eyes had turned dark and unforgiving.
He looked very serious. Seriously upset...with me. With himself. With the world.
"How could you do this?" He demanded.
I nearly choked when I tried to answer him. I couldn't. I was too ashamed.
"C'mon, you little brat. We need to talk," He informed me with a sad tone.
His left eye glowed blue, and we were suddenly in a warm house. His place.
I mentally refused to face my friend. But my body didn't agree. I stood, forcing myself to look him in the cavernous eyes.
Sans sighed and looked down.
I didn't know what to do, so I just watched as he clasped his bony hands over his face and quietly wept.
I finally decided to speak up.
"I'm so sorry," I sincerely told him.
A few moments went by before he became silent.
Sans shakily inserted his skeletal moist hands in his hoodie's pockets and raised his head to speak with me.
I took a deep breath.
"I thought you were my friend, Frisk. I thought you were my brother's friend. He trusted you. I trusted you. Now I know I can't believe you, I can't trust you. Not one thing about you is real. You've just proven that to me, brat. How? Why...did you do this? To Papyrus?" He stepped closer with trembling legs and looked me directly in the face.
  "I...was selfish, Sans. I don't know how to control myself. My hands act on their own accord. I admit it! It's my fault," I cried, vibrating with sobs. I felt a warm liquid rolling down my face.
  He scowled.
  "Darn right it's your fault, you little brat!" He shouted, nearly making the cabin shake.
  "If I could go back, change it...I would," I confessed to him. I refused to to look him in the eyes when I said it.
  "You can, kid...please," he begged, reaching out his skeleton hands to me in desperation. He hard, bony features softened.
  I couldn't take it. After a split-second of indecision, I made a run for it. I rushed out the front door and into the cold snow. A blizzard blew through the frozen wasteland. Snowdin was snowed in.
  I heard the door open behind me.
  "Kid! Don't! It's suicide to run out into a blizzard like that!" Sans loudly cautioned me over the wind, his tone wavering in a confused frenzy.
  Then I saw a blur of white and dark brown.
  I felt a blow to my head. An agonizing hit to the forehead...and the pain was unbearable. I blacked out.
  I saw darkness. I couldn't escape. I didn't know where I was.
  I slowly came to my senses as I woke up.
  The infinite, endless blackness faded away, and I opened my eyes.
  Sans was sitting in a folding chair beside me, peacefully snoring.
  I realized I was laying in Papyrus' bed.
  I also knew that I had a throbbing headache.
  A flyaway tree branch must've hit me on the forehead with the force of one of the skeleton brothers' magic bones.
  I tried to sit up, but immediately felt unsteady and dizzy.
  I moaned in pain as I lay back down.
  He opened his eyes. They were seriously black...but not the serious dark that he had when I killed his brother, Papyrus...it was the kind of void that showed he cared about me. The kind that melted your heart and bore into your very soul.
  Even though I might've taken away his closest friend, he still had a soft spot for me...I could feel it.
  "Are you okay?" He urgently asked when he saw me awake.
"Yeah," I replied, wincing.
He sighed with relief as his white pupils reappeared.
He gave me a weak smile.
"You can't scare me like that, Frisk!" He grinned.
I forced a smirk as he gently gave me a loving squeeze.
I suddenly realized we had to talk.
But how could I sincerely start a conversation up?
And when was the appropriate time to do it?