大奥 [Ōoku] Series by Fumi Yoshinaga

In Edo period Japan, a strange new disease called the Redface Pox has begun to prey on the country's men. Within eighty years of the first outbreak, the male population has fallen by seventy-five percent. Women have taken on all the roles traditionally granted to men, even that of the shogun. The men, precious providers of life, are carefully protected. And the most beautiful of the men are sent to serve in the shogun's Inner Chamber...

Curious about why female lords must take on male names, the shogun Yoshimune seeks out the ancient scribe Murase and his archives of the last eighty years of the Inner Chambers--called the Chronicle of the Dying Day. In its pages Yoshimune discovers the coming of the Redface Pox, the death of the last male shogun, and the birth of the new Japan…

The tale told in the Chronicle of the Dying Day continues as the young female shogun Iemitsu tries desperately to conceive a male heir. But her lover Arikoto seems unable to give her a child, and they must betray their hearts to save their country. Meanwhile, the Redface Pox continues its ruthless progress through Japan, leaving famine, despair, and the threat of anarchy in its wake.

Despite Iemitsu and Arikoto's best efforts, there is no male heir to take over the shogunate. As the Redface Pox continues to ravage the country, it becomes increasingly clear within Edo Castle that Japan's continued existence relies on overturning the centuries of custom that define it!

Gyokuei, who first arrived at the Inner Chambers as a young novitiate monk, has risen to become one of the shogun Tsunayoshi's advisors. He hopes to protect the shogunate the same way his mentor Arikoto once did. But the numerous intrigues of the Inner Chambers—and the shogun herself—are pushing Gyokuei's patience and cunning to the breaking point.

The aging shogun Tsunayoshi must name an heir, but her senile father is blocking the ascendance of the most likely candidate in favor of a young, untried lord. But politics and the shogun’s own unpopularity may soon take the choice out of her hands.

Ienobu's heir is still just a child, and with few official functions to perform, the men of the Inner Chamber find themselves with much time on their hands. Some find ways to make the most of their rare trips outside the palace, while others turn their minds to bloody intrigue...

Yoshimune has secured her place in history as a cunning and capable ruler, but the time has come for her to officially declare an heir. Many in her court hope she will pass over her oafish older daughter Ieshige in favor of the urbane Munetake. Yoshimune has never been one to bow to convention, but this time the future of her country is at stake!

Yoshimune brought many changes to the inner chambers in her time as shogun, and now even after death she brings another: the men of the Inner Chambers must study Western learning and discover a cure for the Redface Pox. For if Japan can’t increase the male population, it’s only a matter of time before a foreign power discovers their secret and invades!