No Game, No Life (2014)

Two siblings are known as the mysterious blank gamers because they never fill in their name. The blank gamers are considered to be the best gamers in the world, having never lost no matter the game. The siblings one day get a mysterious email and end up getting teleported into another world. The God of this world states that their be no wars, no stealing, and no violence; instead everything is decided with a game, any game.