Eiyuuou, Bu wo Kiwameru Tame Tenseisu: Soshite, Sekai Saikyou no Minarai Kishi♀

Hero-King Inglis spends his life ruling and building a great nation, then asks at death for a second chance to live for himself as a warrior rather than a king. The goddess Alistia grants the wish, and far in the future he is reborn as a girl in a minor noble family. The change does not trouble Inglis, but a childhood ceremony reveals she lacks the rune required to become a formal knight. To Inglis this is almost good news: she never wanted status, only stronger opponents and the freedom to master combat. She becomes an attendant to her cousin Rafinha and follows her into training and knightly life, carrying the experience of a previous lifetime and extraordinary physical ability. Every obstacle others call failure looks to Inglis like an invitation to fight something harder.