From Old Country Bumpkin to Master Swordsman

Beryl Gardinant, a self-proclaimed "humble old man," is a sword instructor at his dojo in a rural, backwater village. In his younger years, he dreamed of glory as a master swordsman, but those days are long behind him. Out of the blue, he receives a visit from a famous former pupil who brings him world-shattering news—he's been appointed as special instructor for the knights of the Liberion Order. With his life now turned upside down, Beryl travels to the capital and reunites with some of his former students: elite knights, an ace wizard, and even an adventurer who's attained the highest guild rank possible. <em class=de-emphasized>(from manga)</em>

Synopsis from Anime News Network