Brother and sister Keitaro and Toko Owari are useless NEETs who waste away their days playing video games and eating instant ramen. However, one day, they receive a mysterious invitation which takes them to Kosma, a megalopolis made up of fragments of Earth's greatest cities. In this bizarre new world, they have been given special powers and thrown into a battle royale known as the Genesis Tournament with both their lives and the fate of this new world at stake.