Another World: I Transmigrated into the Demon King from the Start and Covered My Tracks

I was playing games at home when an accident sent me transmigrating to another world. Somehow, I ended up in a pitch-black room, with corpses scattered everywhere. Can someone tell me what on earth happened?!! So no one would find out, I had no choice but to dispose of everything. Well, first things first: I’ll have to make a life for myself here.