Ikatsui Kao de Kyouaku Kishi Danchou to Osorerareru Koushaku-sama no Saigo no Konkatsu Aite wa Shakoukaino Maboroshi no Hana Deshita

Duke Valerio, who is also a commander of the Royal Knights, is having a hard time finding a bride. Due to his fearsome and stern look, all of his proposals end up in rejection. Right when he is about to give up, a meeting is arranged with a daughter of an earl, called the Phantom Flower by other nobles. Despite Valerio's worries, she accepts his proposal right away. Why would the beautiful Phantom Flower choose him of all people? Could she be hiding a secret? A heart-warming love story begins!

(Source: MangaPlaza)