When the world comes to an end, the devil's and human's coexist in the same world to balance the power in the world.If the power balance is shifted either side it can be end of the world.
There is a ranking system in both humans and devil's
In devil's ranking system there is a Nobel,higher,medium and lower which is based on the power
There is another ranking according to the devil's but it is forbidden by the elders of the devil's. That is called slave's where devil's can take the human's as slave's which that makes a horrible thing in the world according to them.
In human ranking system to can be divided into clans .
There are different clans that has different abilities that to save human's from the devil's
Top class clans asura clan, indra clan and vishwa clans.
And there is one clan that which all clan member has been killed by the devil's but there is sole survivor of the clan that has been missing since when the masscare has happened.
There is no one knows about him.
Then the mid range clans are rayya,kammaii,madai and kummarai.
The lower range clans are madhai,mallai,jangallai
These are the clans in the human's