Eiyuu Kyoushitsu S01 E01 (eng sub)

A long time ago, there existed a Demon Lord who terrorized throughout the world until a Hero stepped up to the stage and challenged the Demon Lord, ultimately defeating him and ending his reign. The Hero then created Rosewood Academy, an academy made to help heroes-in-training achieve supremacy and help defend the world when needed that enrolls only the best of the best. Enter Arnest Flaming, a girl with a high sense of duty and the top student at the academy, hence receiving the alias "Empress of Flames" who one day encounters the lively, carefree new transfer student Blade, a boy who seems to equal her in power, something that she finds really irritating. Arnest was then personally requested by The King to supervise, and show Blade around the academy during his stay. The story follows the students' struggles in their quest to become heroes.