No Game No Life - Dai-Ni Shou - Toubu Rengou-hen
The internet is full of rumors about the Neet and Hikikomori genius gamer siblings Sora and Shiro. The two go as far as to refer to the world as a "shit game", but then one day a young man calling himself "God" summons them to parallel universe. There, God has forbidden war, and "everything is to be settled with games".