Standing at a subway station a young man, Kurono (Kazunari Ninomiya), watches as his old primary school friend, Kato (Ken’ichi Matsuyama), attempt to rescue a man who has fallen onto the tracks. Kurono ends up on the tracks with Kato after the man has been rescued, just as a train is speeding through the station. The pair are surprised to find themselves not dead, but rather relocated to a room with a few other people. When they turn around, they see a strange black sphere, about two meters in diameter.
Before they can discover what has happened, the sphere begins to display messages on its surface, including one which lists the name of someone whom they must kill. After the messages the sphere projects two large drawers filled with metal briefcases and strange handguns. They find that they are part of a strange game where they must not only work out how to play, but also how to survive.