Okay, so I’ve watched a few ecchi ऐनीमे time to time ;P, आप can call me a hentai या ecchi but I consider myself an otaku lol…there has been a  couple a good ecchi ऐनीमे that I enjoyed watching like ikkitousen, Queens blade, and one of my all time प्रिय GOLDEN BOY!!!! There are others that are just as good like highschool of the dead that I cannot wait for another season! 
Back to the topic Highschool DxD, I don’t know what DxD stands for my only assumption is the main characters bust size, lmao. So the story from what I get is that the main Male lead is your typical hentai/pervert...