Chaos Head (anime - English subs)

[faceless]

Chaos Head
Takumi Nishijō suffers from intense delusions as a result of his apparent schizophrenia and the extremely secluded lifestyle he lives as a hikkikomori. One day he stumbles upon a gruesome murder scene, a part of a chain of events called "New Generation". He gets caught up in these events and he meets a bunch of increasingly insane anime girls with swords.

This started as a game and later became a manga and anime. I've not watched it yet, but the whole series is there.