At the moment when not even the name of the anime matches the game, you realize the torture that this crap will be... let's go by part as jack would say...
history...? what story? it's crap it explains zero about the plot the rhythm of the anime is horrible and things happen so fast and random that it is... it shows that they didn't adapt anything, neither the game nor the manga, it's simply an "edgy adaptation" that is repulsive as they destroyed everything good about the game...
Animation, musical and design are crap impossible to defend, just google doll frontline m4a1 desing and suffer with that curse weapon...
don't watch this crap it's a waste of time and it's not worth it at all...