Mob devil's guide to surviving DxD

An absolutely normal otaku you could find anywhere gets reincarnated into the world of highschool DxD. unfortunately for him, he has no cheats what so ever. -He didn't meet a bored god that reincarnated him. -He didn't get any blessed cheats. -He wasn't implanted with some game-like system.. -he wasn't lucky enough to get a sacred gear. Nothing. he was an absolute mob. a destined side character. But heaven....or in this case, hell, had not abandoned him. His greatest luck was that he reincarnated as a devil living in the gremory territory. With that as a starting point, he forged a path to the top. using every bit of geek knowledge available, he makes his own legend. No cheats? Only losers cheat. No systems? No problem. I'll make my own. No sacred gear? what is an artificial sacred gear? **** This is my first story, don't be afraid to lay it on me if I write absolute trash. ***