Virgin Knight Who Is The Frontier Lord In The Gender Switched World summary:

After being reincarnated into another world where the chastity and moral values of men and women are reversed and women rule the land, Faust was raised by his mother as a rare male knight. He's quick to become a war hero with many achievements under his belt, but because he inherited his way of thinking from his previous world, there's a certain severe pain in his groin day in and day out when faced with the likes of a scantily clad Queen who may as well be in the nude or the sexual harassment of the well endowed Duchess he calls a friend, among others...