Kanojo ga Koushaku-tei ni Itta Riyuu

the reason why raeliana ended up at the dukes mansion - After a mysterious death, Park Eunha enters the world of a novel. She is revived as a minor character, Raeliana McMillan, who is to be poisoned to death by her own betrothed. In order to break up with her dangerous fiancé, she offers a surreptitious deal to the male protagonist of the novel, Noah Wynknight, but winds up romantically with other men that are not part of the plan.

Noah Wynknight of inescapable but suspicious charm; honest Justin Shamal who loves only one person; or Adam Taylor for whom you have a soft spot for no reason whenever you see him. Will Raeliana successfully get out of this crisis and create a new ending for herself? Who will be the one that will join Raeliana in her new ending?

(Source: Crunchyroll)