Strike the Blood

Strike the Blood (ストライク・ザ・ブラッド, Sutoraiku za Buraddo) is a Japanese light novel series by Gakuto Mikumo with a manga adaptation that began serialization in August 2012. An anime adaptation began broadcast on October 4, 2013.The Anime consists of 24 episodes.

Plot
The Fourth Primogenitor is the world's strongest vampire that should only exist in legends, but he has emerged in Japan with twelve familiars to spread chaos. For the observation and obliteration of this fourth primogenitor, the government and Lion King Organization decided to dispatch an attack mage known as a Sword Shaman. For some reason, the one chosen for the observation was an apprentice Sword Shaman girl, Yukina Himeragi, who is just a middle-school girl!

Wielding the strongest anti-demon spirit spear, Yukina arrived at Demon District, Itogami Island to find the fourth primogenitor. When she finds him, she becomes confused about the true identity of the fourth primogenitor, Kojou Akatsuki. Not to mention the boy cannot remember how or why he is the fourth primogenitor!