Unparalleled Demon Lord

3,000 years ago, the demon land was attacked by strongest entities that exist in the world. But they don't succeed because of the existent of one demon..
He is Demon Lord Zero the strongest demon lord who shakes the world. Simply hearing his name can make anyone tremble! His name is known all around the world.

Now that 3,000 years have passed and the whole world is now at peace, what will he do now?

[ I only created this novel for fun :) ]