Koukyuu no Dansou-hi: Nazotoki Musume wa Koutei no Okiniiri

Suiran, a girl who grew up strong in the mountains, is to enter the harem as one of the 18 concubines. Then, the handsome Emperor Yoshimune orders her to find out the true identity of the ghosts that appear in the harem...!? A Chinese harem fantasy with gender reversal and mystery solving!

(Source: Futabasha, translated)