Saint Dorei Gakuen 3

St. Lilium Academy.
Under the school motto of "Be noble as a lily," this prestigious academy values ​​the independence and self-reliance of its students.
The academy has long produced many outstanding students in the fields of academics, sports, and the arts, but it has a hidden side that must never be revealed.
The Nanjo family.
An illegal continental organisation that engages in various evil deeds, including human trafficking, is said to be controlling the academy from behind the scenes.
The Nishiki family is in conflict with Nanjo.
To the Nishiki family, who have built up strong connections in the political and financial world through the sale of sex slaves, the Nanjo family, who also engages in human trafficking, is a troublesome competitor.
In order to weaken Nanjo's power, Nishiki sends a man as an assassin to St. Lilium Academy.

Translated from the the official site