Fourth season of Strike the Blood.

Barsburg Empire's Military Academy is known for training elites who bring victory to the empire. Students of the academy freely utilize an ability called "Zaiphon" to fight, while the types of Zaiphon usable depends on the nature of the soldier. Teito Klein, a student at the academy, is one of the most promising soldiers produced. Although ridiculed by everyone for being a sklave (German for slave) with no memories of his past, he is befriended by a fellow student called Mikage. While preparing for the final exam, Teito uncovers a dark secret related to his past. When an attempt to assassinate Ayanami, a high-ranking official who killed his father, fails, Teito is locked away awaiting punishment. Only wanting the best for Teito, Mikage helps him escape. Teito ends up at the 7th District Church where he is taken in by the bishops. It is here that Teito attempts to evade the grasp of Ayanami and the Military, so he can rediscover his memories and learn why he is the person that can change the fate of the world. [Written by MAL Rewrite]

60 years ago, a strange case of insomnia struck the population, forcing them to stay awake for more than a full week. The victims, completely sleep deprived, all went mad. To cure this illness, a new medicine was produced, but the side effects turned the patients into vampires. Humanity went to war against this new species and triumphed, but some of the vampires managed to survive. Born from a Human and a Vampire, the main character Mi Liu, "The Child of Hope," is to represent the new hope that will connect the two species. Ringleader of a bank robbery, Mi Liu is arrested and transferred to a special prison of the National Defense Agency that monitors Vampires. Trying to break free with Anji, Mi Liu is attacked by strange monsters and he finds out that the prison location corresponds to the birthplace of Vampires, the old capital "Blue Town." Why are Vampires trapped in Blue Town? What are those strange monsters attacking them? Our heroes must fight to solve those mysteries. (Source: Emon via ANN)

In an alternate universe, shy, awkward Yuki Nagato attempts to court her crush, Kyon, with the help of her best friend and neighbor, the perky and indomitable Ryoko Asakura. Together, the trio defends their high school literature club from extermination…and from the pestering of their over-the-top classmate Tsuruya and her friend and minion Mikuru. (Source: FUNimation, edited)