Yuusha-sama no Oshishou-sama

Overview

While having absolutely no talent for magic, Wynn trained his body every day to achieve his dream, becoming a Knight protecting his country. Compensating his lack of magic with his abnormal physical abilities alone, he entered the school to become knight a few years ago. Until one day, the little girl 2 years younger than him who followed his hard training every day suddenly came back to him after several years. And when that young woman, who became the saviour of the world by defeating the Demon King himself, calls Wynn her "Master," the tale of the "Master of the Brave" knight apprentice begins.

Source: AniList