Outei Denka no Okiniiri: Tensei shitemo Tenteki kara Nigerarenai You desu?!

Synopsis

In her previous life, Countess Ashley was a black rabbit that lived in the Demon Kingdom, but died at the hands of a brave hero. After she reincarnates in the Tolpha kingdom—a country ruled by the descendants of the hero who killed her—the royal prince Clyde becomes her fiancé. It seems impossible as Clyde is Ashley's enemy, but the prince is all too happy to embrace her as his betrothed. (Source: Micro Magazine, translated)