Akujo ga Kishi no Kyouai Kara Nogareru Houhou

The protagonist is reborn into the body of Victoria, the female antagonist in a romance novel, destined to be killed by Cain, her knight who is under a spell causing him to obsessively love her. As the story progresses, the protagonist aims to avoid this fate by maintaining Victoria's role while seeking a way to lift the curse. Initially, Cain's intense and terrifying devotion poses a threat, but his demeanor begins to soften over time.