Undertale Short: Why?

"Do you think that even the worst person can change…?"

The air was cold and silent in the Last Corridor of the castle. Sans' hands twitched in his jacket pockets. He wasn't feeling all that confident. This creature before him had murdered so many peaceful monsters. Sans called it a creature, although it clearly resembled a human. He didn't expect an answer; from what he observed, this creature didn't talk.

"…You shouldn't judge that which you do not understand."

Sans stared at the creature. It could speak?

"…We met before. In another timeline, when we were friends."

It was hard to imagine ever being friends with this creature. Yet, somehow, Sans almost could see himself befriending it. In his mind, he could see a picture of him and his brother making snowmen with it. Watching TV together. Solving puzzles.

If this was all true, then what had happened? What changed?

"We were in peace, on the surface and…"

"That doesn't appeal to me anymore." Sans interrupted.

"I know. You never really did care, you just assumed your end would come before you were forced to care. A true lazy bones, if one ever did exist. But I digress. We were on the surface, when he showed up. I think you know who I mean."

Do I now? Sans pondered to himself, and immediately realized that the creature was referring to Flowey.

"He came and, as promised in my fight against him, he had not retained any memories as Asriel. He slaughtered everyone. I was about to die, when I managed to use what power I had to reset everything. I woke up after having fallen down into the Ruins. He attacked again, laughing at how I had nothing better to do."

The creature paused. It reached into a pocket and pulled out a sharp, gleaming knife.

"If I could have reset back to a time before I had fallen, I would have stayed away from this hell hole."

"F-frisk…" Sans didn't mean for the name to slip out. Memories were just overflowing him. But to give this name to the creature… To give the creature a meaning… "Frisk, we had no way of knowing he'd come back! Don't blame yourself. You didn't have to resort to killing everyone…"

"Who is Frisk?" the creature asked, and then gave a sadistic laugh. "Oh, you mean this vessel I'm using? Frisk and I only share memories and pain. Frisk was never in control, even the first time around. I made the mistake of letting Frisk have their way that time. I allowed Frisk a purpose: To use DETERMINATION in a new way; a way that would give power without actually leveling up violently. Frisk was no more than an experiment for me."

"Who the hell are you then?" Sans demanded, his eye glowing. He was preparing a gasterblaster in his pocket. He intended to kill the creature here and now.

The creature that resembled Frisk didn't look at him. It seemed to be looking past him, as if staring into a void.

"I am the true form of DETERMINATION. I am determined to change the way of the world to fit my vision. Humans… Monsters… Mom… Mr. Dad Guy… Asriel… you were all flawed beyond help. Killing you all is a mercy. I will recreate the world, a world where you do not belong. To let you live in my vision would be genocide," the creature paused and then tilted its head. "But if you must have a name for me, I always did respond to the name Chara."

Fin.