"Ooku: The Inner Chambers" by Fumi Yoshinaga 6 volumes- ongoing
An epidemic wiped out almost the male population reversing the roles of women and men of feudal Japan including the royal family. The shogun is now a woman and in keeping with tradition she also has a thousand of men in her harem or Ooku. Although the title and the basic premise is about a reverse harem it's actually not. It's a saga of the origin and the effect of a disease that affected the country but more specifically the lives of the characters of succeeding generations in the story. Well I've only read just up to the second volume but as far as the story goes it really it's on a different league of it's own. Aside from originality of the theme, I was hooked at the flow of the storytelling of each of the arcs. The characters are all alive with their emotions. I would definitely look out for the other volumes.