Launched in Tokyo, there's an area. In that room is actually really just a world that is black. Periodically, individuals who should have died are transferred to the area. There, they are given weapons and suits by the world, and sends them out on a mission to kill aliens here. While these assignments happen, the rest of the world is unaware to them. These assignments are deadly - participants survive them. The shots are called by the world, also it is not the slightest bit nice. Its name... Gantz.