Responses
Is this what you were looking for?
http://www.mangago.me/read-manga/apocalypse_alice/
YES!!! THANK YOU ε=ε=(ノ≧∇≦)ノ
So I'll try my best to remember the plot....so it starts with this guy joining a school where they train to fight and kill girls who turned into witches or dungeons (not sure) but beyond that the guy also has a sister who turned into one and he wants to save the girls not kill them.
This was pretty vague but I'd appreciate any help (=・ω・=)