Let me tell you that something is very wrong with this story, it doesn't have any logical meaning.

First of all, we have the King of vampires who want to find his"beloved" queen that was sealed because she was too strong (there's a second reason here i don't want to give spoilers) , secondly we have dhampires (half humans, half vampires) who want to kill the King (because he "betrayed" them), then out of the blue aliens are invading earth ( hahaha).
The humans and dhampires need the help of the King to distroy the aliens, and after that they will kill the King and his Queen with the help of "the black swan".

lol. stupid manga