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.

[From DLsite English]