When I Educated the Negative Duke's Daughter, the Results Exceeded Expectations... A Love Story with Prince Ared.

Crown Prince Ared became engaged to 12-year-old Lady Maredia Leterius, daughter of the Duke, when he was 14 years old. However, she was an extremely negative and gloomy lady. This was the result of her younger sister Elena being constantly favored in the Duke's household, while Maredia was continually disparaged by her parents. Crown Prince Ared made a decision: he would guide Maredia toward becoming a bright and cheerful lady. Four years later, on the day of the marriage announcement with Maredia, Elena comes forward claiming that she would be a more suitable marriage partner. What will be Maredia's attitude at that moment? Will she be able to respond to Elena properly?