Kore Ga Mahoutsukai No Kirifuda

Rikus, a skilled swordsman, is deeply tired of the bloody battlefield, so he fakes his death in battle and retires. He enrolls in the Magic Academy to make a new start at life, but he has zero aptitude for magic, and he struggles along with Shino, a recruited student who enrolled with him.

"Let's work together at the academy tomorrow!"
"That's gross. Please shut up."

......Undeterred by the strangely cold Shino, Riks overpowers the wizards with his physical skills as a swordsman! He unintentionally overturns the traditional teachings of the academy one after another. The princess, who has been taking notice of his fighting prowess, recruits him into the army!

(Source: Fantasia Bunko, translated)