Please recommend an ancient romance novel.

The female lead was a saintess of a country, the state preceptor, or the witch. The female lead often went out disguised as a man and met the male lead. Was the male protagonist a prince or a lord from another country? He seemed to have six or seven sisters. He had been learning from a master in the female protagonist's country since he was young, and then he had a junior sister and a senior brother. I only remember the plot: the male protagonist was drugged and then in a cave, the female protagonist lost her virginity to the male protagonist in order to help the male protagonist dispel the aphrodisiac. However, the male protagonist did not know at that time, but the male protagonist made a mark on the female protagonist's neck, and the male protagonist knew the female protagonist's identity. Later, the female protagonist married a prince of a country on behalf of the male protagonist's junior sister, and the male protagonist escorted the female protagonist to get married. In the end, he did not expect the male protagonist to be the cold-faced prince of that country. The female lead and the male lead's sister got along very well and would sometimes read their fortunes.