Your pov
You remembered it like it was yesterday. It isn't really a pleasant memory.
Flashback
You were pushed down MT. Ebbot by some bullies in your school. You were the first human to fall. You met asriel,toriel,asgore,gaster,undyne and alphys. You were only 12 years old. You were good at science so you ended up being gaster's lab assistant. You became friends with asriel,alphys and undyne, asgore and toriel became your adopted parents and gaster is kind of another father to you. Gaster then made two skeletons. One named sans and one named papyrus. When they were created, you ran tests on them but not the painful kind of tests, it's just like if he can do this or not. Sans grew up and he treated papyrus as a brother and gaster as a dad. Sans became another lab assistant of gaster. He was smart but you were a little smarter but gaster is the smartest. Then one day, the core had problems. Sans,gaster and you tried to make the core stable but, gaster ended up falling. You caught him and he survived but that caused you falling in the void instead. They became smaller and smaller until you only saw black. You were in the void. Now, you had cracks on your face. It's like a scar. It's starts from the right cheek to the right eye. Your left hand had disappeared and still had small bits floating. Your soul had a crack in the middle and it lost its trait. You had a permanent smile on your face. You were stuck in the void until nowFlashback end
You teleported to snowdin to see how sans,gaster and papyrus are doing. Gaster had completely done the machine to save you. He turned on the switch but, it didn't work. You can't be saved here. Well it is possible but they still haven't found a way yet. You checked on sans to see him and papyrus is guiding the human through a puzzle. You smiled. Sans looked at you and stopped walking. He was shocked. You then disappeared and went on top of the tree where he can't see. He shook his head and catched up with the other two. Only gaster and sans remembered you. You watched the three as they proceeded to solve puzzles. You teleported in the ruins to see Mom reading a book. You teleported to the castle to see Dad watering the flowers. You teleported back to the void. There ain't much to do here. You just stood there.
Sans's pov
I still haven't forgot about (y/n). She fell in the void. I was supposed to confess my feelings to her but, she fell. We can't do anything. I thought I saw her there earlier, staring and smiling at us when we were guiding frisk through puzzles but, it was just my imagination. I really missed her. Just now, gaster told me that the machine didn't work. We worked on how to get (y/n) back in the lab. We worked overnight with alphys.
A few days later...
We were working until alphys yelled. "GUYS! THE HUMAN IS KILLING ALL THE MONSTERS!" we rushed to the monitor to see the human stepped on Papyrus's skull. My soul shattered at that moment. We planned on what to do.
A few more hours later...
Gaster died earlier in the fight and now,I got slashed. "Welp. This is it huh? Just... Don't say I didn't warn ya." I walked away. I saw papyrus and gaster there, smiling at me. "Pap, dad. Do you... Want anything?" I turned to dust. The human already defeated asgore and the weed.
I turned into a ghost and saw everyone there. We were watching the human. They all hugged me. I hugged back. Then, something weird happened, (y/n) appeared. She looked, glitched. "❄👇✌❄💧 ✋❄✏ ✋💣 ❄✋☀👈👎 🚩👉 ✝✌❄👍👇✋💀☝ 🔆🚩✝ 😐✋😞😞 ❄👇👈💣 ✌😞😞✏✏✏ (THAT'S IT! IM TIRED OF WATCHING YOU KILL THEM ALL!!!)" She teleported to the void with the human and entered a fight. I was scared. Not her too! The human grinned wide and creepily sliced her. It didn't affect her? It goes right trough her. She shot bones and gaster blasters fast with a difficult pattern to match. The human hit her and (y/n) turned into the human and when the human sliced her, the human's hp decreased by 19. They dodged they attacks as best as they can. They ate burger but, it decreased their hp by 0.5. their hp is only 0.5. (y/n) shot many bones and blasters. The human is weak. They only have 0.000000000001 hp. (Y/n) grinned and pierced a bone through the human. Before their soul can even break, (y/n) grabbed it and it turned into a monster soul. She looked at us and smiled. She split the soul into multiple parts and it floated towards all the monsters here. The ghost version of the weed appeared in front of me and it turned into asriel.
I woke up in the judgement hall with gaster. I checked my soul and it's only a small piece. It is starting to become whole. A few seconds passes and the soul is whole. I looked forward and saw (y/n) smiling at me. She summoned her soul and it cloned. Her soul was a bit smaller. The other soul doesn't have any trait. The others ran to the judgement hall. Before they can speak, they saw (y/n). "W-who-" before they can ask who she is, she motioned us to follow. We followed and she lead us to the barrier. The other soul floated to her and the other soul went to the barrier. The other souls followed. The barrier cracked and it was broken. I cried because I missed her so much. When I was about to say a word, she disappeared. There was a note on the place she stood. I got the note and read it aloud.
Dear everyone,
My name is (y/n). I'm sure you all don't remember me. I wanted to thank you all for being kind to me when i fell down. I returned the favor and broke the barrier. Please, stay safe.P.s sans and gaster, don't even try to save me. I know you want to but you can't. I'm sorry.
I read the last sentences silently only for me and gaster to hear. I felt tears coming in my eyesockets and I cried silently because (y/n) can't come back. The monsters cheered and rushed out of the barrier. I and gaster are the only one left inside. "Sans, I know that it's hard but, we can't do anything to save her." "We still can! I know that if we work hard enough we can save her. She'll come back." I cried. (Y/n) appeared in front of me. Me and gaster stared at her. I stood up,ran to her and tackled her to a hug. She patted my back. " FØrg3t ãbôŪt M3 sāñs. Mōv3 øÑ fōR m3 pl3ãsË." Her voice was glitchy. "No please! Come back!" "ĪM SøRrY" she disappeared without a trace. I cried. "Please. It's hard without you." I sobbed and gaster tried and comfort me. "Please."
Wow... That.... I'd be lying if I said I didn't cried. Well. Half lying because either didn't cry but I ALMOST cried. If y'all want, I'll make a part 2. Comment down below if ya want.