Rule Harem? Let Me Farm

Palace selection takes girls from good families and puts them in a place where the only skill that matters is knowing what not to say. Diana arrives there having grown up dark and heavily built, nothing like what a lady of her class is supposed to look like, treated by her own family as a burden to be moved along. Among the delicate beauties of the harem she is the obvious outsider, and she makes it worse by having no interest in the scheming at all. She would rather grow radishes. She says exactly what she thinks, to everyone, including people it is dangerous to say anything to. That bluntness turns out to be worth something. The Emperor comes to trust her more than anyone else around him, precisely because she has never once shaded the truth for advantage, and a General hardened by campaigning finds himself attached to her as well. Then war breaks out. The court needs the Emperor's attention elsewhere, the harem uses the gap to move against her, and Diana is left inside the palace with an Empress's title and no weapon except saying what is true.