Oukyuu wo Tsuihousareta Seijo desu ga, Jitsu wa Honmono no Akujo wa Imouto da to Kidzuite mo Mou Osoi: Watashi wa Kachi wo Mitomete Kureru Koushaku to Shiawase ni Narimasu

The Saintess Clarice is suddenly cast aside, engagement broken off by the prince. Now her sister Lycia is set to marry him. On top of all of this, Clarice is now made to marry the prince's brother, Duke Alto, who is said to have a horrendous face. Upon arriving at the estate, it was clear that the darkness cast around the duke's face was truly horrifying enough to take one's breath away. With how things have been with his face, Duke alto has spent his life as a recluse, closing himself off from all who would try to reach him. However, Clarice seems to be the first to change something within him. For the first time, there seems to be hope for the future as the two begin to grow close to one another. (Source: MangaPlaza)