Angura is a shortened form of the english word 'underground'. This is a cultural movement in Japan that dated back to the 1960's and had a great expression in independent theatre.
It is a movement who influenced many manga artists who tried to find a unique identity for their own cultures.
It also linked with the Eroguro style, but the main difference was that angura is darker and more formal. The use of Japanese uniform, kimono, or other traditional garb is very common in angura-kei bands.
Inugami Circus-dan is a band that falls into the genre of Angura-Kei