Shokuetsu Ninpouchou ~Mugen Zecchou, Ishukan Jigoku~

The House of Getsuin and the House of Kyoso: In an age when ninja still existed, two clans went to war. Sakuya and Ayane of Getsuin were victorious over Natsume, the leader of Kyoso. However, that was not the end. So consumed with revenge was Natsume she opened the gates of hell, which unfurled and spew forth like a maw all the unspeakable things of its bowels. The House of Getsuin was decimated. Sakuya and Ayane were spared death for an acme fate far worse.