
Kojou Akatsuki's days as an ordinary high school student in the Demon District of Itogami Island come to an abrupt end after a fateful encounter leaves him with the remarkable abilities of a vampire. It isn't long before he is thrust into the center of attention when it is discovered that he is the fourth primogenitor, an immensely powerful vampire whom most consider to be merely a legend. Fearing Kojou's destructive potential, the Lion King Organization sends in an apprentice sword-shaman, Yukina Himeragi, to monitor, and should he become a threat, kill the boy deemed the world's most powerful vampire. Forced together by circumstance, the two form an unlikely alliance as Kojou comes to terms with his abilities and they both struggle to protect the city from various emerging chaotic forces.

Itogami Island is a manmade island in the middle of the Pacific Ocean where summer never ends. A high school student at Saikai Academy, Akatsuki Kojou, is on his way home from studying with his classmates, Aiba Asagi and Yaze Motoki, when he notices a girl in the Saikai Academy middle school uniform following him.

Yukina moves into the room next to Kojou's. When Kojou sees that she only has a bare minimum of furniture and necessities, he takes her to a hardware store. Kojou's younger sister Nagisa also insists on hosting a welcome party for Yukina, adding up to a very lively day.

The morning after the battle against the Combat Deacon and his homunculus, the town is left in ruins. Yukina had been shocked to see how vastly Kojou's power exceeded that of the Familiar, but now she learns that Kojou can't even control his own Familiars. Kojou and Yukina pursue the escaped Eustach and Astarte to an abandoned laboratory, where another intense battle awaits them...

Eustach and Astarte continue their assault, finally launching an attack on the central support of the manmade island. When Kojou learns that Asagi is trapped inside, he's eager to save her, but his inability to control his own Familiars holds him in place. Unable to see him go on like this, Yukina makes a suggestion he never expected...

It's nearly time for the Saikai Academy ball sports tournament, and Yukina and Nagisa are all fired up to act as cheerleaders! And thanks to the workings of Motoki and Rin, Kojou and Asagi are paired up to participate in the badminton doubles match for their class. Meanwhile, Natsuki is occupied with the capture of some therianthropes that have appeared in the warehouse district, and someone is targeting the Fourth Progenitor again...

Kojou and Yukina meet Dimitrie Vatler, a nobleman who shows an abnormal degree of affection toward the Fourth Progenitor, and Kirasaka Sayaka, Yukina's old friend also under the employ of the Lion King Organization. When Vatler proposes that Kojou capture some terrorists hiding out on Itogami Island and Yukina volunteers to take care of them instead, Vatler challenges Yukina to test her suitability for the task. And, though Sayaka has always been a friend of Yukina's since childhood, her behavior starts to change...

In her excessive defense of Yukina, Sayaka launches an attack on Kojou, but he can't control his powers. Yukina's arrival prevents the situation from growing dire, but Yukina leaves them both on the school roof to think about what they've done.

Gardos the terrorist has reawakened the ancient weapon, Nalakuvera. Kojou and Sayaka barely escape with their lives, but they fall into the depths of the manmade island. Asagi hurries to analyze and control Nalakuvera while Yukina fights a fierce battle to stop Gardos.

The trouble with the Black Death Emperor Faction has been resolved. Kojou has returned to his daily life with Sayaka as a new acquaintance, but he can't decide whether or not he should reveal his vampiric nature to Asagi. It's around that time when he meets a friend of Nagisa's, Kanase Kanon, known as the middle school saint.

Kojou and Yukina prepare to ambush Possession Mask, the group responsible for the attacks around Itogami Island... but one of the Possession Mask members they see is Kanase Kanon.
Available on: AT-X