If you're looking for manga similar to Urareta Oujo na no ni Shinkon Seikatsu ga Shiawase desu (Light Novel), you might like these titles.
Maria Martini, the daughter of a baroness, is contractually married to Count Ricardo Ricœur for one year only. Ricardo's wife has been unfaithful to him and left him, and he has been repeatedly honey-trapped by women who want to marry him again. Maria's role was supposed to be a cover to protect him, but during the course of their life together, Ricardo's behavior became strange. The first thing that comes to mind is that Ricardo's stepdaughter, Lydia, is very interested in her new mommy. A contractual marriage begins a too-happy married life.
Two babies of different statuses were swapped by fairies. Raised as a noble, the 13-year old Anna became an adult. She who doesn't resemble her family at all, worried every day because she couldn't use her magic that well. One day, a fairy appears right in front of her...
Angelique's engagement was annulled by the second prince for the crime that she did not commit. Furthermore, by the order of the king, she will be married to the impoverished Count Sergei, who lives in a remote region. What awaits her on her way to the frontier is a very poor estate beyond her imagination and a handsome count!