Sorceress Empire ~Teiritsu Mahouin~

The era when magic declines gradually and is about to be replaced by science and technology. But there are still "demon" race monsters living on the outskirts of the empire and organizing skirmishes at border guards.
Hero is a battle magician responsible for three failure students. They have personal conditions that prevent them from learning normally. You have a year to train them into excellent witches.

[From vndbreview]