I have a feeling I know who she's cosplaying as, but the name of the series escapes me.
I’m guessing she’s a demon because of those horns, but isn’t she wearing a miko’s kimono as well? Or maybe a variation of the traditional shrine maiden?
I can’t help thinking she looks a lot like Kagami from Lucky Stars though.
Guesses are greatly appreciated!
EDIT: Thanks to Sachi for commenting this is Hanyu from Higurashi no Naku Koro ni!