Reincarnated as the daughter of a poor Baron, Estella has to work as a tutor to ensure her family well-being. She is hired to tutor the Duke's half-siblings, who are killed by their older brother in the original novel.

Estella decides to change that outcome, and strikes a bargain with the Duke. So long as Diego, the duke, doesn't kill his half-siblings, Estella will keep it a secret that Diego killed the previous duke. They seal their deal in a contract.

Everything goes well until the novel's original heroine comes to Estella, and asks Estella to help her get a contractual marriage with Diego. Estella agrees to help the original heroine and tries to connect her with Diego, but this time, Diego doesn't react the same as in the novel.