No Game, No Life Vol. 2 (Manga Edition)

Sora and Shiro - brother and sister - are brilliant (but unemployed) gamers whose fame has spawned urban legends all over the Internet. One day, they are summoned by a boy named 'God' to an alternate world. There, God has prohibited war and declared this to be a world where 'everything is decided by games' - even national borders. Humanity has been driven back into one remaining city by the other races. Will Sora and Shiro, the good-for-nothing brother and sister, become the 'Saviors of Humanity' in this alternate world?