Tsuyo Sugite Yuusha Party wo Sotsugyou shita Saikyou Kenshi, Mahou Gakuen demo Aisareru

The manga centers on Leon, the magic sword user who defeated the demon lord. He decided to move with the changing times, and elects to leave the hero's party in order to study the new ways of magic at one of the kingdom's seven magic academies.

(Source: Anime News Network)