Momojiri Taiiku Onna Kyoushi

Aoi Takazawa, a physical education teacher, is feared by both men and women alike for her unbelievably strict attitude. She is so upset with Shuichi, the main character, who was observing her PE class as usual, that she raises her hand against him.

Shuichi is determined to turn this arrogant and violent female teacher into a sex slave. As he gradually trains her by threatening her, he discovers that her rear hole is her weak point.

Shuichi, gaining momentum, spends a lot of time torturing her there, and his actions extend to spanking, restraints, and other hard play, as well as public training in the swimming pool.

At first, Aoi is defiant, but she can't resist the pleasure that these acts bring her, and eventually she begins to seek them out herself.

Aoi's M sensibility, which had been hidden deep inside her body, comes into full bloom, and she comes to know the pleasure of being bent over by a certain master.

[From official site]