Help finding a manga

Hi all, i was wondering if anyone knew a manga where the fl is in marriage with a duke?,but he already has a lover who is like a singer/dancer(I remember her having long black hair). They get married but the duke spends all his time with his lover in a different house. The fl says in the main house with the servants, who hate the lover, and grow to like the fl. Whenever the duke come back to the main house the fl pretends to be a maid and the staff kinda help. I think it was black and white and might have transitioned into colour? Also remember the duke having brown hair. Thanks again!(￣∇￣")