The Duke of Mount Deer (1998)

Wai Siu Bo is the son of a prostitute who works in a brothel in Yangzhou. After joining the Heaven and Earth society, he heads to the Capital and gets enrolled into the service of the Grand Eunuchs. There he becomes friends with the young emperor Hong Hei (Wai mistakes the emperor as another young eunuch) and falls in love with the emperor's younger sister, Princess Kin Ning. His adventures in the Forbidden City leads him into discovering the empress dowager as an impostor; finding several volumes of the prized 42 Chapters which contains the location of a treasure cave; helps the emperor kill the baddie courtier, Lord Obai; and see his position rise from humble eunuch to a grand courtier and confidante of the emperor.