An otaku's journey to become true Emperor God(first world is high school dxd)

An otaku died for saving million and trillions of of people's from a insane terrorist nuclear attack. But he reborn in high school dxd world as rias Gremory's twin brother with a system . So now what will he do? Become lost in plotline? Or change the world to his own convenience? Let's go and see ourselves what his fate lay himself to... --------------------------------------------------------------------- Note: English isn't my first language so if there's grammatical error and misplaced then please comment. I will try to to become better... so corporate. Note:- first eight chapter is full of mistake and I'm going to rewrite them.... Near future. Note:besides zero most of all carracter belong to there respective owners. Note: Help me put this tages... Harem, wincest, op mc