The Apothecary Diaries, Volume 6 (by Natsu Hyuuga)

Maomao has proven her worth to the denizens of the palace time and time again, but she's got her work cut out for her on this occasion! When the ever luminous Jinshi asks for Maomao's help in disguising himself to take care of business outside the palace walls, Maomao must dig deep to mar her employer's heavenly charms! And to make the ploy believable, Maomao herself is roped in to a spot of theater as Jinshi's companion. But Jinshi's 'business' takes him right to the gates of the pleasure district! Has all Maomao's hard work been for a mere assignment, or is there another mystery afoot '