むすめーかー

Itsuki is a university student. One day, his father suddenly dies and he takes over an orphanage his father once ran. There live various girls in difficult circumstances. The orphanage looks normal at first sight, but it is actually a brothel. He needs to train and make them sex slaves to pay off the debt his father left. His new life as their "father" and "trainer" now begins....

[Translated from Getchu]