KORO SENSEI QUEST!

Spinoff of Ansatsu Kyoushitsu and continuation of the anime film short. In this world, Koro-sensei is the Demon King while the students of class 3-E are cast as heroes who must defeat him. The students learn swordsmanship and sorcery at Kunugigaoka Magic School. Their strange adventure begins! (Source: Official page) — Description from AniList community (anilist.co).