Moto Ansatsusha, Tensei Shite Kizoku no Reijou ni Narimashita.

A former assassin named Serena is reborn as the daughter of a duke after failing a mission. She finds it difficult to adjust to noble life, especially with her mother's erratic behavior and her adoptive sister's manipulative attempts to undermine her. Serena manages to avoid conflict at social gatherings and navigates the complicated dynamics of school life, but her aloof attitude causes her to be shunned. After learning her adoptive sister is engaged to the second prince, Serena flees her home. She is then confronted by the first prince, Evan. The story follows Serena, who has no experience with love, as she moves forward in a foreign aristocratic world in a tale that mixes humor and light romance.