GANTZ:O

After dying in a subway station, teenager Masaru Kato wakes in a Tokyo apartment with other recently deceased people and a mysterious black sphere called Gantz. The machine gives them weapons and sends them into battles against invading aliens in Osaka, turning their strange second chance at life into a fight governed by strict rules. To survive, Kato must take part in the missions, confront the monsters and earn points alongside the other unwilling players.