Rikan Koukoku Hikikomori Zuichou Hiden: Hibi Koukyuu wo Nukedashi, Yuunou Kanri Yattemasu.

The reclusive consort took only five years to climb up the ranks and become a court official. Leading a double life, the consort dresses as a man to solve all of the many challenges the empire faces! But her true identity behind both masks is a Japanese woman called Saya who had been transported into this Eastern-themed world, where black is considered the color of nobility. Bored of the luxurious and uneventful life of a consort, she dresses up as a man and sneaks out of the harem to work as a court official! She'll have to hide both her hair color and identity while she navigates the royal court and the dangers that threaten the nation. (Source: Tokyopop)