I bring sans to the waterfalls. Peace and quiet. We both sit down on the bench remembering our first date. There was still some ketchup on the ground. You both sat there in silence. I was snuggled up against sans. Him falling asleep right as I did.

??? POV

I was walking and I saw them. They where snuggled up against each other. She'll pay for taking him from me! She will pay. Luckily it was my time to shine. I took out my knife strapping y/n with it multiple times and laughing as I did so. HA HA she can't love him know.

Sans POV

I woke up to see y/n with a bunch of blood and cuts. Those idiots. I pick her up once again teleporting back to the house and I sit her on the couch. I feel her pulse...nothing. I quickly call Alphys up. As soon as she gets her I let her do what she must. I sit in the living room waiting... Then there was a knock on the door. I get up and pull the door open to reveal Frisk and Chara.
   "We want to see y/n" Chara says "I know you did it to her!" I shout. I fell Alphys tap my shoulder. I look around to face her. She was sitting there tears strolling down her face. She wrapped me in a tight embrace "I-I'm so s-s-sorry" she cried. "Do you know who did it?" I ask knowing it was Chara. "Yes, with her DNA and blood and stuff like that I found the finger prints of... Frisk" i look over to frisk. Why would she. "Frisk" I cry "why" "SHE STOLE YOU FROM ME" she says. I stood there, Frisk has feelings for me. But she KILLED someone I loved just to get to me, that bitch should be BURNING IN HELL. My right eye turns blue and I start tossing Frisk around until her soul shatters and it was just me, Chara, and Alphys. I broke down sobbing "why" I sob "first my bro now my girl friend" then suddenly I see smoke appear out of no where "sans I think I can solve your problem" I hear a familiar voice say then it's gone like nothing was ever there. It was probably my imagination.
   Later I fell asleep on my couch sobbing about how life was going to be without y/n.

   I woke up in a dark room seeing a figure I walk towards it. "S A N S" it says it a glitchy voice "dad" "Y E S  S O N" "what, what is it?" I ask "I  C A N  H E L P  Y O U  G E T  Y/N  B A C K" he says "how?" I ask wiping my neon blue tears off my skull. "Y O U L L  H A V E  TO  T R A V E L  T H R O U G H  D I F F R E N T  T I M E L I N E S" Gaster starts " I F  Y O U  M A K E  I T   T H R O U G H  E A C H  O F  T H E M  A L I V E  Y O U L L  G E T  Y/N  B A C K, I F N O T  Y O U L L  B E  B A C K  H E R E L I K E  N O T H I N G  H A P P E N E D"

Comment witch time line you want first

EX. Under swamp

Enjoy!