Because it needs one.
1st question: What is the connection between Rachel and Ragna? She bit him and that makes him half vampire?
LOFNL. 
She bit Ragna as a kid and sort of bugs him from time to time since. May or may not have anything to do with Ragna having the power of Azure.
Cool.
Is she the “Slayer” of the BlazBlue universe?
What do you guys think of the True Ending?