Souls are registered on the Death List (Kiseki), and when their time in the living world is over, they must appear before the Lord of Hell (Enma DaiOh) for judgement.

Sometimes the souls of the dead refuse to show up. It's the job of the Summoning Division (Shokan) to collect these missing souls. This division is also responsible for making sure the number of unscheduled deaths (from murders, supernatural forces, and the like) doesn't get too high. This involves going into the Land of the Living to investigate suspicious deaths and collect souls that should have died but for some reason haven't, ensuring that all souls can appear before the Lord of Hell at their appointed time.

Members of the Summoning Division are known as Shinigami - Gods of Death. They are the highest-ranking operatives in the Afterlife (though sadly underpaid...)