Strike the Blood, Vol. 5 (manga)

Asagi, Yukina, and Nagisa have been captured by the Black Death Emperor faction. Kojou and Sayaka go after them, breaking into the island they suspect of being the terrorists' base. But an ancient terror awaits them--the Nalakuvera. A new beast vassal stirs within the Fourth Primogenitor, but will Kojou's power be enough to save his friends?