The Crossdressing Bold-Spirited Lady and the Womanizing King

In the history of a certain country, there was a king who was said to be an extremely womanizer with over three hundred illegitimate children. In the same era, there was a lady who lived a free-spirited life while disguising herself as a man. These two were not in the relationship of king and official mistress, but were said to be friends of the opposite sex. Even though they had three children together. A story of these two that has disappeared into history.