Gantz

Two friends are run over by a subway train. They suddenly find themselves in a strange apartment with other people who have also just “died”. While everyone tries to understand their presence in this place, a mysterious black sphere appears and orders them to eliminate one by one the super-powerful creatures.
After trying to rescue a man on the subway tracks, two teens wake up in a room dominated by a mysterious black sphere that sends them to hunt down and kill aliens hiding on Earth.
The only way to resurrect is to kill.