Sans's pov

I  started to have flashbacks of me and (y/n) together. Of how we met, what we did and stuff. It was fun. I soon woke up. I'm still on the floor. It doesn't hurt anymore. I groaned and sat up. I was dizzy but it soon faded. I looked at the table and to my relief, the soul is still there. I grabbed it and I'm finding something that can make a trait but no luck. I sighed and I knew the only thing that can make a trait is the rainbow potion. I went back to the table and put some in the soul. It glowed rainbow. There are still some leftover potion. I took it and I was going to get out but I heard a screech. I fell to the floor and the potion glass broke on my skull. It poured on my jacket and the human soul. I felt pain again. It poured on my soul. It was a lot. The potion on my skull went to my soul as well. I felt so much pain. I can't handle it. It took a few minutes for the pain to fade and I was tired again. I tried and fight the tiredness but I fell asleep again.

I woke up and stood up. I took the soul and there was no leftover potion. I sighed and went out. I'm too tired to teleport. I was in alphys's lab and I only saw dust. Wait... No! Please no! Don't say that the humans went on a genocide route!!! I ran to my house. My legs are tired and I can't run. I just hurried there and saw dust. I hurried back and I went to new home. No body's there. I hurried to the throne room. No body's there. I hurried to the barrier and it was, broken? The barrier is broken! But where are they? I put the soul in my pocket and hurried outside. I sat on the ground to take a moment to look at the sunrise. It was beautiful. I looked at it until the sun was fully up. I had the energy to run again so I ran. I saw a town full of monsters but, no humans? That's weird. I saw a sign and read it. "WELCOME TO SURFACE HOME! THE TOWN WHERE THERE ARE ONLY MONSTERS AND US FAR AWAY FROM A HUMAN VILLAGE! "
(p.s. our king still sucks at names)

I chuckled at the last sentence. I tried and search for anyone but I can't. I decided to ask one of the monsters. "Hey! Have you seen some other tall skeletons here? One is wearing a scarf and one is wearing a lab coat?" "Oh! Papyrus and gaster? Yes! They are in a meeting right now in the human village but their house is right there!" The monster said pointing to a house that is colored orange,blue and purple. "Thanks" I said and ran to the
house. I looked in the window and nobody was there. I teleported inside and saw a picture. It was a picture of all of them except for me. They were in a field.

(Sry can't draw mettaton EX >_<')

It looks like their having fun. I looked around and things were the same. I went upstairs and saw 5 rooms. The other one is Papyrus's. I can tell because he has some stickers on the door. I opened the next door. It's gaster's. I opened the next door. It's (y/n)'s room? She lives here? Oh well. I opened the next door. It's empty. I saw a paper. I read it.

Sans's room. We hope we find him soon.

I put it back. I opened the other door.

It has a plain design. I'm guessing that this is the guest bedroom. I teleported outside. I explored the town. I soon found the king and queen's house and undyne and alphys's house. Wait... I looked at one of the calendars. 'September 2020' I WAS OUT FOR 3 YEARS?!?!? WHAT?!?!? BU- HOW?!?!?!? DO THEY EVEN REMEMBER ME?!?!? AAAAA!!!! I started running around until I calmed down. Okay okay... I will just go back home... Sheesh. How is that possible though? A paper flew at my face. It looks old and fragile. It's a missing poster of me!!! They have been looking for me!!! I ran and saw papyrus,gaster and (y/n) are going home. I ran and they already went inside. I knocked on the door. Papyrus opened the door and looked shocked. "SANS!!!!!!!" he shouted. He hugged me tight. I hugged back. "IM SO GLAD YOUR BACK! I THOUGHT THAT WE WOULDVE LOST YOU!!!" gaster and (y/n) went to the door. They saw me. Gaster hugged me and (y/n) just stayed still. I hugged them and they let me go. "OH!!! COME IN SANS!!!" papyrus said and carried me inside. He put me on the couch. (Y/n) and gaster teleported inside too. I smiled. "So sans. Where were you all along?" Gaster asked and I remembered the soul in my pocket. "I was in alphys's true lab and I collapsed there for 3 years because of a potion. By the way, did (y/n) get her soul back right now?" I asked and gaster sighed. (Y/n) just kept her head low. "No." I held out the soul to them. "Well I have made a soul in there." I said and gaster got the soul. "How did you-" "I saw (y/n) do it." (Y/n) attempted to glare at me. She can't feel a little mad so she can't glare at me. "Did you follow me and asriel there?" She asked. Her voice is like a bored voice. "Yes. Don't ask. I need to keep an eye out for ya." "You stalker" she said. Gaster gave her the soul. She took it and stared at it. She put it in her chest. It went through. She smiled. "I can feel again!" She said and hugged me. I hugged back. And then something happened. I saw her old soul. It was shining bright. She let go of the hug and stared at the soul. It came in her chest. She summoned her soul and saw that her soul was the normal (s/c) but it has a rainbow aura. She returned it. But wait... What about my soul? The potion went to my soul. What happened to that? "Umm gaster?" "Yes sans?" "I used that rainbow potion to make that soul to have a rainbow trait and it was poured on my soul twice. It made me pass out. What happened to that?" I asked and gaster summoned my soul. It was a rainbow monster soul that is glowing brightly with a blue aura on it. "Incredible. The rainbow soul has six traits. It has DETERMINATION,BRAVERY,JUSTICE, KINDNESS,PATIENCE,INTEGRITY and PERSEVERANCE. You are the first monster to survive determination without melting or dying. Even in those timelines." Gaster muttered the last sentence loud enough for me to hear. I put my soul back in my chest. Papyrus gasped. "CAN I GET DETERMINATION TOO?" "umm.... Pap.... I think you are too young to get determination." "BUT IM ALREADY 18!!!" "to get Determination you need to be 30 or something." Papyrus groans. I just made that excuse up because I don't want a melting or dust brother. Gaster knew that and chuckled. "Since sans is here, let's party!!!" (Y/n) said and we all agreed.

Your pov

You got your phone and got in a group chat. Perfect. Everyone's online.
(Y-you- T-toriel A-asgore U-undyne Al-alphys )
Y-hey guys!
Everyone-Hey!
Y-So we are planning a party. We are inviting you all to it! It starts at 10 am here at our place. Wanna come?
A-sure
T-Ok
Al-i will bring noodles!
Y-okay! Bring lots of it. We need food too. Who wants to bring pizza?
U-i will but, what's the party for?
Y-its a secret~ Hehehe.
U-umm... Okay...?
A-is it okay if I bring tea too?
Y- of course! Bring any food you want!
T- I will bring pie!
Y-Okay. Cya all at 10! Bye!
Everyone-Cya!
Chat ended...

You quickly dialed (f/r) (fav. Restaurant) "Hello! This is (f/r) at your service! What can we get you?" "I would like Spaghetti, Milkshakes, Burgers and (f/f)(s) please!" "That will be 153.75!" "Okay! Bye!" You said and hung up. You looked at the clock. It's exactly 8:00 am. You have 2 hours to prepare. "Alright! Go and prepare yourselves for the party!" You said and ran to the bathroom to take a warm bath.