Board Thread:General Discussion/@comment-26173711-20160917200205

In the Genocide route, during his battle he mentions that he stopped caring because he knew everything would end.

At the end, Chara gives you the chance to either erase the world or not. After choosing whether or not to erase the world, they offer to "restore" the world. But why would you restore a world that hasn't been erased?

Because Chara already erased it.

And Sans battles you to try and prevent that from happening.

"But Sans knows about SAVE!"

He does. But in my theory, why would you reset everything? You came here to kill. So replaying would have no real value to it.

"But what if Chara means restoring as in resetting?"

Then by that point you would have no choice but to erase it. If Sans does know the truth behind Chara, then no matter what Frisk wants, the world will always be resetted. Again, he's trying to keep you from resetting the world in the Genocide route. He's trying to keep you from meeting Chara, and erasing the entire world.

But that's just me, I hope you enjoyed reading this :) post your ideas and such below, I would love to read them! 