It's a story about one character surviving and living in a world held sway by a supposed god who believes said world wishes for the moset evil and depraved life imaginable. The anime follows the events leading towards the realization about why the world is so fucked up and how such monstrous feats are capable by man, but it doesn't get explained. The manga expands upon and details it all more closely, while the anime cut alot of the specifics out. Recently it's gone to almost complete shit since the main character gathered some sort of group of child heroes following him around. Untill that point it had been him with a supporting cast who weren't meant to stay like they are now. It's been running for a very long time as the author is notorious for waiting a year or longer just for one chapter. It also gets released in the young animal magazine i'm not sure if that's still true today though.