why raeliana ended up at the duke's mansion manga

Raeliana ended up at the duke's mansion because she made a deal with Duke Noah Volstaire Wynknight, the male lead in the novel world she was reincarnated into. After being reincarnated as a character destined to be poisoned by her fiancé, Raeliana sought to avoid her fatal ending. She pretended to be engaged to Noah in exchange for protection, leveraging her knowledge about the royal seal, a secret critical to the royal family. Her fiancé was the one who intended to kill her to take advantage of her family's wealth, but Noah, as a duke and the king's younger brother, offered stronger protection and political influence. Thus, Raeliana moved to the duke's mansion to be officially engaged to him and to secure her safety and her family's future.