Clive Barker's The devil's school dxd (male reader x dxd harem)

Y/N Galloway is a descendant of Patrick Galloway, at an early age his parents sent him to St. George's monastery to protect their son from the supernatural. but when Y/N starts to grow up, he always dreams about a strange green stone and also a girl with red hair. when Y/N has reached his majority, the great master of the monastery of St. George gives the task to the hero to go to Japan and find out about the supernatural in one of the academies of Japan, as well as to find out from a traitor who stole something from the abbey, and maybe find out something about his strange dreams.