Help finding a manga

It has a medieval-like setting.
She has to get married to a nobleman (Marquis, Duke, I can't remember) she meets for the first time during the wedding ceremony, held without guesses and without wedding party.
He has a bad reputation, he's told to be a cold scary evil bad person. Actually his father was that, to the extent he killed his own wife (the ML's mother) and kept his son locked up in his room until his own death. The ML is a kind guy, he's not cold but very shy. During their first night he remains hidden under the sheets and communicates with her writing instead that talking.
Please, help me! Thanks in advance!