teisou gyakuten sekai no doutei henkyou ryoushu kishi

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...

- Quote from MangaDex.Org