DISCLAIMER TIME! I don't own Undertale, which belongs to Toby Fox!
Well... it took me some time...but now I've begun to get into Undertale. Everyone else is getting into the lore, so... why not? As for me, I think Undertale is a pretty fun game... almost like a 'Choose Your Own Path', in a way! Anyway, hope you all enjoy this story... for those who did the Genocide route (which isn't a good route, by any means), you all could probably take a guess on what this story is going to be about! Anyway, enjoy!
Sans just watched as the human, known as Frisk, slashed his brother Papyrus into dust as his head fell off. Sans just couldn't believe what had just happened that he temporarily lost his smile. He just couldn't believe what just happened. At first, Sans thought that the human just walking through the puzzles was just kidding around and just making Papyrus angry on purpose... but Sans started to have his suspicions. After all, aside from that Flowey character, he remembered everything that happened before...
FLASHBACK
Sans sighed as he looked down. None of the other characters aside from that flower that he rarely talked to knew what was going on, but Sans did... the minute the kid entered their world. He was in a time loop... an infinite loop that looked like it would never end. Sans couldn't explain it, but sometimes when the kid... died, he would suddenly find himself in different places... in this case, this time, he was near the beginning of the loop as he waited for Frisk to come out.
Sans gave a smirk, even though Frisk knew about the whoopee cushion trick, Sans still had a bit of fun with the kid anyway... but for some reason, Sans sensed that something was off with the kid. Like... the kid he was looking at was the same, yet... somehow, he was different. He didn't even attempt to hide behind that conveniently placed lamp, which threw Sans off a bit... but it still worked out as Papyrus just... ignored the human altogether and walked off. Sans blinked in confusion, but just accepted it like nothing happened.
It wasn't until the kid was walking through the puzzles towards Papyrus that Sans knew something was... off. He couldn't explain it, but for some reason, he knew that kid looked different. Once the puzzles were all done, he told Papyrus not to get near the human for a while and told him to wait for him at their place while he went to check on Toriel.
Sans walked all the way over until he reached the basement of Toriel's home. It was then he noticed... the dust and pieces of a broken heart. Sans passed it off at first as a random monster kill (which was perfectly understandable, since at least in some loops, Frisk would kill at least one or two monsters to see what would happen... and Sans always judged Frisk for it based on his LOVE), but as soon as he came upstairs, he noticed that there was no sound... or smell coming from Toriel's home. Sans started to go into denial, maybe Toriel was at that flower garden near the hole on top of the ceiling, watering them.
Sans may have been one of the laziest, but he was pretty quick when something seemed off. As he walked quickly passed the obstacles, he realized that there were no signs of any of the random monster encounters that usually roamed around. As he kept walking and zooming, he noticed dust everywhere... which made Sans even more worried as he eventually got to the point of the flower garden... but his fears confirmed it when Toriel wasn't there.
"this can't... can't be happening..." Sans said in worry as he pulled out a cell phone and dialed Undyne's number.
"Yes, what is it?" Undyne said bored, over the phone.
"undyne, ma'am, this is sans!" Sans said, worried.
"Sans? Brother to that braggart of yours... you sound a little tense. Unusual even for you." Undyne said, noticing that Sans was gasping in worry.
Sans sighed. He didn't feel like warning everyone about the human, since people usually figure it out on their own... but this kid was being a menace! He had to say something. "undyne, listen, there's a human roaming around our world!"
"A human? Oh, how divine! Asgore will be pleased to hear there's another..." Undyne said, pleased.
"no, you don't understand! this human is no ordinary human! when i met up with it, something about that human seemed... off! like it didn't care what was going on... it even passed through my brother's puzzles... more like ignored them, but besides my point! i thought something was off with the kid, so i went over to toriel's place... she's dead! toriel and every creature that was in her area is dead!" Sans said, worried.
"What? Please tell me you're joking!" Undyne said, surprised.
"i saw dust fragments and pieces of a broken heart! does that'SOUND like a joke?" Sans said worried.
"If what you say is true, Sans, then..." Undyne sighed. "I'll tell everyone to evacuate and hide in a safer place. If you're right about this human, then... I'll get everyone to evacuate Snowdin and warn everyone else immediately!"
"you better hurry. who knows how many more creatures the kid killed!" Sans said, worried as he hung up the phone. Sans frowned in determination. He made up his mind. He was going to go back to his brother and warn him about the kid.
Of course, by the time Sans arrived back at the house, he opened the door and looked around as he called, "papyrus! we have to get out of here now! that kid that ignored your puzzles, he's a maniac! papyrus?"
It was then that Sans noticed a note on the fridge as he took it and read it. "SANS, I HAVE HEARD FROM UNDYNE AND EVERYONE ELSE THAT THE KID THAT WE MET HAS BEEN KILLING EVERYONE... BEING A MEGALOMANIAC! BAH! I DON'T BELIEVE IT IN THE SLIGHTEST! I JUST THINK THAT THIS HUMAN IS LOST, FRIGHTENED AND CONFUSED! I MEAN, IT'S PERFECTLY NATURAL, RIGHT? SO, I, THE GREAT PAPYRUS, HAVE DECIDED TO CONFRONT THE KID, TELLING HIM THAT HE DOES HAVE A FRIEND WHO CAN HELP HIM TO GREATNESS! HE WON'T DO A VIOLENCE, I JUST KNOW IT! SEE YOU UNTIL THEN... THE GREAT PAPYRUS."
Sans smile started to wilt as he turned around. With Frisk being what he is now... what's stopping him from killing his brother. "no!"
Luckily, since the timeline started to loop, he knew EXACTLY where to go... and he knew where Papyrus and Frisk were...
But by the time he arrived... he was too late.
END FLASHBACK
Sans could only watch as Frisk used his foot to crush Papyrus's skull before moving onto the next area. The blue jacket wearing skeleton then went over to the dust fragments that was Papyrus as he looked down, broken. "brother... why? why did you have to go over to the kid?"
Sans growled as he took the dust in his hands and hugged it. "kid... why? he just wanted to be your friend... what happened to you that made you... like this?"
Sans frowned as he gave his sinister smile and got up. "i don't care what it takes, i will find a weakness somewhere, you will be going down kid! you will pay for hurting my brother..."
Sans nodded as he got up and put his hood up, looking down at the dust that was once Papyrus. "brother... i will avenge you... toriel... and anybody else he happens to kill. no more being a lazybones... mercy is off the table..."
Sans then started to walk off towards no man's land, knowing that when Frisk eventually met Sans over at the judgement hall... Frisk was due for a big surprise...
But at the same time, Sans just couldn't shake the feeling off that Frisk wasn't... who he was. Even though he knew he was weak... his attacks were actually pretty strong... even if he had to cheat his way in... he'll find a way to make the kid pay... oh, how Frisk will pay...
And that is this Undertale one-shot out of the way! How did you guys like it? Yeah, I know that this character is named 'Chara', but after watching some fan animations of Sans, Chara and Frisk each singing a parody of the Steven Universe song 'Stronger Than You', I decided to make the story like this, so either way, I hope you all enjoyed it as is! Anyway, thank you all for reading, and have a great day!