In Edo period Japan (1603 to 1868), 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 to a quarter of the total female population. 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 Chambers.

Oooku won an Excellence Prize at the 2006 Japan Media Arts Festival, the 13th Tezuka Osamu Cultural Grand Prize along with Gekiga Hyouryuu in 2009, and the 56th Shogakukan Manga Award in the Shoujo manga category in 2011. The series also received a special prize at The Japanese Association of Feminist Science Fiction and Fantasy's fifth annual Sense of Gender awards in 2005.

The series was published in English as Oooku: The Inner Chambers by VIZ Media under the VIZ Signature imprint from August 18, 2009, to March 15, 2022. It has also been released in Spanish by Ediciones Tomodomo since April 22, 2024.

The manga was adapted into a live-action film that was screened in 2010. Two television drama adaptations aired in 2012, and another in 2023.