Du Gong's Adopted Son: I Forcibly Married My Sister After I Ascended the Throne

Is There an Old Saying About a Male Protagonist Who Looks Gentle on the Outside but Is Actually Very Sick and Crazy?

It is best for the male protagonist to be gentle and elegant on the surface and easy to push down. The female protagonist can be more forceful, and then the male protagonist can be extremely possessive of the female protagonist behind her back.