Tensei Reijou ga Kokuou Heika ni Dekiaisareru Tatta Hitotsu no Wake (Light Novel)

17 years ago, a "genius" female knight unknowingly lost her life after being unable to protect a 7-year-old prince who was third in line to succeed the throne and got wrapped up in a war of succession between his two older brothers. That female knight has now been reincarnated as the Countess Flora, and she retains all memories of her past life. She speaks about her past life to no one, and always felt obligated to try to stay away from the royal palace... But the former prince - who has now become king - suddenly comes to her and directly orders her to be his personal guard?!  Between being manipulated and being doted over, what will happen in this life between the unmatched swordswoman and His Majesty the King?!