One Day, My Sister Died

Story

After her sister turns up dead as the latest bride of a monstrous, exiled prince, Louanne is assigned to take her place and hopes to uncover the truth. The prince initially refuses her, but with her magical powers, she begins to heal his pain each night while concealing her own. Meanwhile, her evil uncle, who took advantage of her ability in order to run a medical scheme at home, begins to crumble. Has Louanne truly escaped her cursed family, or is she stepping into something darker at Sable Manor?

Synopsis via AniList (English).