M-ogui: Last Order.

Anime adaptation of the same name manga by Kurosugi Shinsaku. Rina and Shiori are two women who are not to be messed with. One night, when out late in the karaoke bar, the staff of the karaoke bar tries to take advantage of the two ladies. There is a disagreement about the bill, but the two ex-gang ladies fight back. As revenge they decide to rape the karaoke staff and force them to have sex with each other.