This paper examines the recent hit shojo manga by Yoshinaga Fumi, Ooku: The Inner Chambers, which creates a science fiction alternate version of Edo-period Japan ruled by a female shogun. This gender-reversed world is the outcome of the sudden outbreak of an epidemic that kills only male youths in the era of the third shogun Iemitsu. In the inner chambers of Edo Castle, which are the private space of the shogun, 3,000 beautiful men live and work. This alternative world rereads existing historical narratives and also provides a critical space for readers to examine the multiple discourses of gender and sexuality. The paper approaches this re-representation of Japanese premodern history in the genre of shojo manga from several angles. To provide a fuller understanding of Ooku, it shows how revisionist presentation of the Tokugawa inner chambers in a 1960s Yoshiya Nobuko novel provided a model for a subgenre of historical period drama in post-war popular culture. It also examines shojo manga traditions of non-normative gender identities.