For some people rank is an important thing in the bleach role playing world. Always having something to shoot for is great motivation to do the best you can on all accounts. To keep things as realistic as possible, we have made it a bit more difficult to gain rank than it normally would in any other guild.
For shinigami:
As you know the three main ranks within the soul society are captain, lieutenant and 3rd seat. Of course 3rd seat will be the easiest to gain. Once you join the guild and your character is approved, unless told that you are captain or lieutenant, you are a 3rd seat officer. (Unless Division has its Third seat Taken.) In some guilds this would be the bottom of the barrel but here we pride ourselves in our 3rd seater's. They will have a specific role in the story and who knows they may end up saving the day.
Next we have the lieutenants. This group generally has complete control over their shikai and are training to gain their bankai. In order to gain this rank you must prove your valor in combat as well as you intelligence in the lieutenants test that will be issued Via PM by the commander.
The final rank to achieve in the bleach shinigami world is that of captain. In order to gain this rank you must pass the written captains exam as well as reveal your bankai before the captains.
The Arrancer:
As cruel as this seems, it's real. Once you are created you have achieved the rank of arrancer. This is an important yet low rank, meaning you will be first to battle and possibly first to die, but this could be avoided. The only way to gain a rank into Espada is to kill an espada so that a rank becomes open.
