Reijou Kyoushi Eiko "Inbaku Sekkan"

Professor Eiko is the daughter of the late founder of the Academy. As Vice Executive, she is put in charge of reforming the school, which is quickly losing its funds. The job isn't easy, however, what Eiko does leaves her despised by even the most outrageous of teachers. Based on a background investigation, teachers who were found to have an interest in SM take her into a secret training room and confine her there. It was there that the terrible acts began. In the end, while being taped on camera and receiving double penetration, Eiko's masochism suddenly comes to light.

[From DLsite English]