Frisk had all the power in the world to stop the bone from hitting Sans. But was it their right to do so? If this whole situation was so hopeless, was it really in Frisk's place to make Sans keep going through it? The Frisk that Sans was friends with...was long gone. In its place was this husk of a person, ruining things for everyone. A powerless, hopeless, shell that made things worse for everyone. That was how Frisk saw themselves now. So when that bone pierced through Sans's heart, Frisk simply watched it happen. They let the level of their sins crush them with guilt as their feet were once again rooted to the floor. Flashes went through their head as they remembered killing Sans the first time and realizing, it hurt far more to watch Sans do the 1 point of damage himself.
*So I'm not going to bother.
*The underground? The other monsters? The surface world?
*I just can't keep caring about that anymore. This world doesn't concern monsters of any kind.
*Only brats like you.
Frisk's weapon falls from their hand and tears begin to fall from their eyes. As Sans keeps talking, every now and then glimpses of Chara are evident in Frisk's expression. No matter how many times Frisk played through this world. This time...this moment...Was the last time the Frisk they knew themselves as...would exist.
*I hope you remember me for as long as you live.
*When you build your castle of bones and dust I hope that you toss and turn every night
*And remember how you drove an honest guy like me
*To their death.
*Because that's when I'll return.
*And we'll both burn in hell.
And with that, he was gone. That sinister smile still plastered on Sans' face, he dissolved from the feet up into dust and blew away with the wind. Frisk could hear the sound of their own heartbeat, quickly beating, it was pushing out all the remaining determination Frisk had left. Their guilt, their sadness, their outlook on life, was slowly pouring out of Frisk with each beat of their heart and being replaced with emptiness. Chara was getting closer. They could feel it.
On the ground where Sans had been was now...just a coat covered in dust. Lying in a crumpled ball on the ground Frisk used the last of their energy to step forward and put it on. The color draining from their skin as they walked closer and closer to the coat. They didn't speak, they didn't think, Frisk simply put the coat on.
It was heavy.
Only fit for someone carrying the burdens of the entire world on their shoulders. A role that now belonged to Frisk. Frisk closed their eyes and fell into the darkness of their own mind. Their soul, already gone to chara, Frisk willingly let the determination seep from their body, and returned to the powerless little child they once were. Chara reset the world for Frisk and carried out another genocide run. A run in which, Frisk had no control over. They just watched as the monsters were all slaughtered once again. The coat seemed to make Frisk impossible to be hit anyway, but the most haunting fact that kept Frisk from fighting back was that...Sans, was nowhere to be seen. Papyrus didn't seem to think he had a brother, and no one else in the underground even knew a skeleton by that name.