Tousatsu Kyoushi to Joshi***sei

Mr. Todou is a pervert voyeur school-teacher.
One day as he was watching his video collection he had an idea.
He decided to target three students...
loving and gentle Chika who dotes on her little sister,
meek and shy little Kurumi,
and the bad girl of class, Fubuki.
This is the story of his approach to them... and their fates...

[From DLsite English]