Read manga: Eiyu-Oh, Bu Wo Kiwameru Tame Tensei Su, Soshite, Sekai Saikyou No Minarai Kisi

manga
Summary:

King Inglis, who lived for his country and people, strongly hopes that in his next life, "I want to live freely and pursue the path of the warrior." The wish is heard by the goddess who reincarnates the king into the far future but in the form of a cute girl! Moreover, it is declared at the age of 6 that she is incapable of being a knight even though she is the daughter of a Master Knight.