Nina, who lost her parents in an accident, is taken in by the Roost family and lives as a substitute for their daughter, Lilia. She accepts this role, thinking it's only until she graduates from the prestigious magic academy, but her life as a substitute takes a big turn when she receives a request to treat Prince Erland's magical abnormality!! Nina is forced to be a substitute and spends her days feeling restricted... but she's not as meek as she seems!? A school fantasy begins, as she earnestly looks forward and lives her life!