Kokoro o Tozashita Koushaku Kakka to Kon'yaku Shita Hazu nanoni, Nazeka Taisetsu ni Sasete Shimattemasu!

A romantic fantasy about a cold-hearted duke with a closed heart and a brave, but misfortunate girl!

In place of her half-sister, Countess Alicia Marino, who is unable to use magic as she does not possess the blessings of spirits, marries Joel, who is rumored to be a cold-hearted duke.
Joel has a cold attitude toward Alicia, who is rumored to be selfish and man-crazy, but contrary to the rumors, Alicia is hard-working and kind-hearted, and Joel gradually opens his heart to her.
https://www.cmoa.jp/title/283834/