MAGICAL WARFARE

"I'm sorry... I turned you into a magician!" Takeshi Nanase, a high school student in the regular world, meets Mui Aiba, a girl from a world of decay, and finds himself caught up in a grand magical war. It's a war to help Mui, a war to save the world, and a war to change destiny. The curtain rises on this modern tale of authentic magical action. (Source: Kadokawa) — Description from AniList community (anilist.co).