From MangaHelpers:

In ancient Japan, the Shogun established the Ooku, a harem of beautiful females, to give birth to and raise the heir to the throne. But 400 years later in a timeline slightly different from ours where the military empire still exists and Japan is still closed off from the rest of the world, the Ooku is in chaos. What used to be full of gracious and refined ladies, the girls now are violent and rude. They do as they please, get themselves into shenanigans and wreck havoc around the castle! [vyc]