Athena-blood twins

Intro so this is in my au(and yes you can add characters from other anime like kny or whatever anime you want),choose your name,your sisters name is Athena,both of your childhood was great until your parents were killed and the killer threw the knife in front of you and the killer soiled you with blood so she thinks you did it and hated you since then,its now just you and her,and she wants to go to another universe,will you change things (and if she does in the real game you dont have the thing on your head,youre the girl who has white hair and shes the one with black hair,youre 18 shes 21 and your uniform is not revealing