Kojou Akatsuki lives on the artificial island of Itogami, and he has a secret: He's the "Fourth Primogenitor," the most powerful vampire in the world. He's carefully kept this dark knowledge from his family and friends, but one day, a beautiful girl named Yukina Himeragi appears before him and tells him that she knows who he really is--and that she's been sent to...kill him?!
THE REVIVAL OF THE TRUE FOURTH PRIMOGENITOR IS NIGH! When Kojou Akatsuki was a junior high school student, he met a vampire named Avrora...and then he saw her again when travelling to the hospital to visit his sister. When Kojou learns this mysterious, quiet girl could be the key to saving Nagisa's life, he helps her escape the Magna Atraxia Research lab. With the arms dealer Zaharias planning to use Avrora in his Blazing Banquet, can Kojou stop the revival of the true Fourth Primogenitor and save Itogami Island?
Kojou and Yukina help Natsuki Minamiya by trying to capture the "Masked" appearing in the skies above Itogami City, but one of the Masked turns out to be Yukina and Nagisa's friend-Kanon Kanase. When Kanon disappears, Kojou and Yukina go after her, but fall into a trap set by the mega-corp Magus Craft and find themselves abandoned on a deserted island...
He never asked for this power. Kojou Akatsuki used to be an ordinary high school boy--but that wasbefore he became the Fourth Primogenitor, the most powerful vampire of all time. Worse--he doesn't even remember how it happened. Middle schooler Yukina Himeragi, meanwhile, is the Attack Mage sent to observe him--and to stop him if he gets out of control. But was it really a good idea to send a cute girl to observe a massively powerful vampire boy whose abilities activate whenever he gets aroused? And on an artificial island populated with all manner of demonic individuals, each with their own designs on the Fourth Primogenitor--?!
Nagisa has collapsed! Kojou rushes to the hospital, but suddenly a mysterious girl appears, and she looks just like Avrora, the former Fourth Primogenitor. She backs Kojou into a corner--but is she the real Avrora? Through this encounter, Kojou regains his lost memories, what will he remember? Finally, Kojou's past and the secrets of the Fourth Primogenitor are revealed!
When all the students depart for a school field trip to the mainland, Kojou is delighted to hear that he'll finally get a chance to be free of observation for at least a little while, whereas Yukina has mixed feelings about the whole situation. But events move quickly when an alchemist by the name of Kou Amatsuka appears, with the goal of reviving the holy grail of alchemy--a liquid-metal life-form known as "Wiseman's Blood." As the crisis deepens, even Asagi becomes involved when this alchemist's relic grows more and more uncontrollable. What can the world's strongest vampire do?!
A New Year on Itogami Island is right around the corner, and for Kojou and Yukina, that means cutting off their contacts and returning to the mainland for a top-secret rescue mission. Coincidentally, this also means zero contact between Yukina and the Lion King organization. Can the fearful duo see their mission through to the end, or will they be overwhelmed by an unexpected enemy?
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?
At the invitation of Dimitrie Vattler, emissary of the First Primogenitor, Kojou and Yukina attend a yacht party. Dimitrie's guardian has it in for Kojou, and as though that's not bad enough, the festivities turn serious when Kojou and Yukina discover a terrorist plot that threatens Itogami Island itself...