Board Thread:General Discussion/@comment-26173711-20160917200205/@comment-25648422-20160917230046

Hmmm, if you ask me, I doubt that Sans knows about Chara. Chara was present before the war between humans and monsters began and Sans and Papyrus probably did not exist during that game. But in my opinion, when they did, it was never hinted in the game that they had knowledge about Chara. In the Genocide Route, we all know that Sans engages in a ferocious battle with the player in order to stop them from disrupting the timeline. But it doesn't imply that he knew Chara but that he merely knows that he has to fight the player because he knows that they would disrupt the timeline and probably repeat the same actions they did in the Genocide Route over and over again.