Why Raeliana Ended Up at the Duke’s Mansion

After a mysterious death, failed university student Rinko wakes up as "Raeliana", the daughter of a wealthy family in a novel she has read. However, Raeliana is a minor character who is destined to get killed by her fiancé in the near future. Armed with her knowledge of the novel's plot, Raeliana/Rinko sets out to break off the engagement. Her plan brings her to the most powerful duke in the country and the novel's male lead character, Noah, with a deal; "Pretend to be my fiancé, just for the next six months."

Synopsis from Anime News Network