DanteMustDie
Google translate - Personal opinion: why make Harry know that at Hogwarts? when you have made a crossover of HP, DxD and Persy Jackson (if I remember correctly) when there are four more renowned schools in the world and other magical groups and factions out there and staying in the school will only be "used" by Dumbledore as a martyr as happened in the novel / movie you could even make Harry enter into a contract apart from the one he has with Rias which gives him knowledge about other magical systems out there (not for nothing is the heir to one of the satans) if with all that demons live, your library must have things that could be useful to you