The Fallen Lady is Secretly Marrying His Majesty

Diane, a former count's daughter who has lived in a convent since her parents died in an accident, rushes to Lord Ibert's manor when she learns that the mysterious gentleman who has been supporting her for the past seven years is in critical condition. However, his illness was just an excuse to summon her, and Lord Ibert is actually the emperor, Victoire! He asks her to marry him in secret to break the curse that brings misfortune to the emperor's bridal candidates. Diane accepts his plea for help. "You can let loose..." Melted by his sweet whispers and caresses, Diane's shy body gradually opens up. But then, unnatural accidents start happening to her, too! Source: MangaPlaza