Reijou Elizabeth no Kareinaru Migawari Seikatsu

Elizabeth Magnus, from a minor noble family facing financial difficulties, is taken in daylight by an unfamiliar man named Sylvestor. He mistakenly believes her to be his missing sister, also named Elizabeth, due to their striking resemblance. After realizing his error, Sylvestor offers her a deal: she will impersonate his sister for six months, or until he locates the real one, in exchange for financial aid for her family. She agrees, beginning her life as Elizabeth O’Brien, a noblewoman.