Yandere Sans X Reader

the jist of it all

Obviously you fell down a hole. And you met a skeleton and his brother and yes frisk was your brother and you were on a quest to save him. But one thing led to another and thing started to get wierd with sand. Your good friendly relationship just got darker. He would become more angry and violent when others were close by. He was clingier. He even started picking fights with papyrus. You started to get freaked out. Let's say the friendly skeleton had a dark side that no one knew about and it was just starting to come out and it sure as hell ain't pretty.