This is an AU where THIS Sans is OVER *you starting Genocide runs in the timelines. So, he turned on *you. Instead, HE starts the genocide run, but its not called that... Instead its called *SAVE. *You would have to save everybody from HIM. He does this so that *you can feel his pain. He started out as nice and defensive of his brother like every other Sans, but the violence got to him. Also, he's a 16 year old skeleton. This was inspired by the song Darkside by Grandson. Song here: https://www.youtube.com/watch?v=KUNjh1IIPpg