Saikyou no Kenjin, Henkyou no Mura Musume ni Umarekawaru.

Once, a war of invasion was waged across the entire continent by an evil empire. The great hero who defeated the emperor and ended the war was Edgar Knightsward, the "Sword God." However, even he, hailed as the world's strongest swordsman, could not overcome old age. In the end, he entrusted everything to his disciples and closed the curtain on his 70-year life. But when he came to, he had been reborn as a village girl named Linne living in a remote frontier of the country!? A new legend begins, starring Linne — the former world's strongest swordsman, now a little girl! *Source: BookLive, translated*