Keikoku Akujo no Yarinaoshi Oujotan: Kichi Danchou ga Bukiyou de Hanaremasen

The villainess who almost destroyed her kingdom found herself looped back to five years before her death. She is a fourteen-year old girl, loved by her father, the King, and her two brothers. Sophia remembers everything that she had done, to her maids, to her knights, to her family. Bryath, her bodyguard, was loyal to her until he dies at war that she and her brother Riley started. She decides to save everyone including her, in this life. Everyone was aghast when Sophia told them she'll start studying for the kingdom. She is determined to be a real princess for people, not villainess, in this life. Now she must uncover all conspiracies to avoid the tragedy. But something is off about Bryath... he is too protective in this life!? (Source: MangaPlaza)