Shinigami are essentially people who are put in charge of taking care of the dead.

Like humans, they all are unique, and have different skills. They also have different rankings, and homes.

The order from lowest to highest:

Civilian

Private
Private 2
Private First Class
Specialist
Corporal
Sergeant
Staff Sergeant
Sergeant First Class
Master Sergeant
First Sergeant
Sergeant Major
Command Sergeant Major
Sergeant Major of the Army (Queen/Commander in Chief/M'Lady)

Second from the top, Command Sergeant Major, has only one person, Isaac Gerakobits, a soulless shinigami.

He works under Lady Diame, their leader. He delivers, follows, and proceeds with commands.

Then there are medics, Like Jay.