I'm pretty sure they want to cover up to:
Epic 4th war, and end it with Kisara killing the first of her hated enemies.
How long were they going to do this, 13 episodes or 26? If it's 13 then yes, the plot will progress incredibly fast - so fast in fact, that you might be better off reading the LN. I personally think that it was a much better medium than anime to present the true grimness and despair of Black Bullet.