Based on the erotic game by Liquid.

It is the job of Ryunosuke, a pedant, to train women to his client's liking. When he receives a request from the chancellor of St. Martius Academy, he is assigned three beautiful girls. He sets up beautiful twin sisters, Sakura and Fujine, and the young lady, Wakako, in a trap, and Ryunosuke teaches these innocent virgins how to handle men's sexual desires. It was a series of extreme acts of training, including gang rape and servitude to classmates. Involving Miyu, a slave student, and the chancellor's secretary, a fearless sexual feast began at the sacred school!

(Source: Parabook, translated)