I started watching Ooku on a whim and got through it over the holiday. (It's only 10 episodes!) It's about an alternate history of Japan where a plague wiped out most men and continues to keep the population gender-imbalanced, and women began to take over their roles in society. The story centers on the Ooku, the male harem of a female shogun.
( mild spoilers below )
( mild spoilers below )