Futa Majo

There is a Private Magic School located in the depths of an unknown forest. The students are descendants of the first wave of wizards that flew from their world 400 years ago, driven away by the demon lord.
Naoya studies there surrounded by twin sister students. They say that Naoya is the container who now inherits the soul of the legendary Devil. Both white and black witches start a battle over his powers. At the same time, Naoya uses his sudden magic power to do mischievous things to the girls.

[From vndbreview]