The Diary of a Middle-Aged Sage's Carefree Life in Another World: Volume 5 by Kotobuki Yasukiyo

Despite monster attacks, backfiring experiments, and one very overzealous guard, the students of Istol Academy of Magic have made it most of the way through their training camp. But it’s not over yet—and a trio of assassins have emerged to kill Zweit, who’s been separated from the rest of his group.