Onna Kyoushi x Choukyoushi ~Houkago no Ura Jugyou~

The protagonist of this story is a very unremarkable, normal student, even in class. One day he drops his mobile phone by accident, and by that coincidence he ends up being drawn in by the evil powers of his teacher, Minami Akira. Following that... she targets a girl who is the same class as our hero, making two victims. The days of Minami's assault and training have begun... !

[From DLsite English]