Kaminari Tei to Yobareta Saikyou Boukensha, Majutsu Gakuin ni Nyuugakushite Issai no Enryonaku Musou suru

Noah Oukrate, the S-Rank Adventurer known as the Thunder Emperor. As instructed by his master, the witch Sherah, he gets enrolled in a magic academy. There, he meets the daughter of the Duke, Claris, and the son of a fallen noble's house, Arthur. While working hard together with his classmates such...

Source: MyAnimeList