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 as the A-Ranked adventurer Claris, he continues to be unrivaled at the magic academy with his thunder magic by his side! — Description from AniList community (anilist.co).