Another World : Vampire?

Deep in our world there's another world
Hiding in shadows, creeping inside the darkness of humanity, lies a shadow world where demon-blooded and angels-blooded creatures walk among us in different dimension at the same time. They could see through us, but we can't see through them. When the world is in the verge of collapse, they will fight to bring the balance between the shadow world and the human world. To keep us from the secret of the world that will lead us into an eternity war

This is their story
And this is how it began