Kojou Akatsuki (暁 古城(あかつき こじょう) Akatsuki Kojō) is the male protagonist of the story. He is the older brother of Nagisa Akatsuki and the childhood friend of Yuuma Tokoyogi. Although he appears to be a normal high school student studying in Saikai Academy, he is actually the fourth primogenitor; the strongest vampire in existence, an immortal demon thought only to exist in legends. He became a vampire and the fourth primogenitor only three months before the beginning of the story. For much of the story, he cannot remember how he became a vampire and gets an intense headache when he attempts to. Yukina Himeragi is sent from the Lion King Organization to observe him and to eliminate him if he is deemed dangerous.


Kojou is 16 years old at the beginning of the story. He has dark silver-blue hair and blue eyes which turn red when he is either aroused or angered. He is usually seen wearing the Saikai Academy school uniform which consists of a white button up shirt and black pants. He also wears a blue under shirt and a white hoodie. Since he is a vampire and tends to avoid daylight, he has fair skin. He has well-toned muscles and a "well-endowed" body.


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Kojou is a kind, empathetic person, who goes out of his way to help others. He is also an intelligent, sly and carefree individual. When angered, Kojou becomes quite fearsome adversary. Kojou has indomitable willpower, supernaturally strong charisma which has attracted the attention of both admirers and allies, allowing him to even befriend his enemies. Kojou is shown to care and worry about his sister a lot. He is however generally oblivious to the romantic feelings that others have of him due to his strong siscon nature.


Kojou was a normal human until he first met Avrora the 12th Kaleid Blood and became her blood servant, a pseudo vampire. Since then, he spent his daily life with her but those days didn't last long until she ordered him to destroy her and became the fourth primogenitor. In addition, he lost his memories regarding the incident and the days they spent together. However, he later regained some portions of it after fighting Giada, the third primogenitor disguised as Avrora using the No.14 Grimoire in attempt to recover his lost memories. He fully regained his memories alongside Asagi after Yukina performed a ritual on them.

He first met Yuuma when he was trying to retrieve Nagisa's hat which was stuck on a branch at the end of a cliff. He looked for Yuuma at her regular spot where she used to hide and watch both siblings everyday and asked for her help. Without waiting for a respond he quickly grabbed her hand and got back the hat together. However, after they did so Kojou nearly fell off the cliff only to be saved by her, he later thanked her and said that she's pretty strong. A while later after everyone introduced themselves. He first met Motoki and Asagi during middle school.

He first met Avrora at Fairy's Coffin. Kojou use his body to protect his sister and Avrora from the terrorist attack leaving him on the verge of death. Avrora admired his courage and turned Kojou into her blood servant. Avrora ordered him to destroy her alongside "Root" and chose him as the 12 Kaleid Blood's successor.


The Right Arm of the Saint

Returning from a study group, he senses that a girl is following him. He tries to lose her, but then spots her being harassed by demons. A fight ensues, and Kojou steps in before things escalate further. He then catches a glimpse of her panties and she leaves in disgust, but drops her wallet. Inside contains her student ID and name, Yukina Himeragi.

They meet again the next day, where she explains her task and the significance of him being a primogenitor. One night, the two head to a convenience store, when an explosion occurs. They investigate the source and discover Rudolf Eustach and Astarte. They began to battle, but it abruptly ends when Kojou loses control of his familiar.

From the Warlord's Empire

The Amphisbaena

Labyrinth of the Blue Witch

Fiesta for the Observers

Return of the Alchemist

Kaleid Blood

The Tyrant and the Fool

The Black Sword Shaman

Bride of the Dark God

Kojou receives an unusually heavy package from Dimitrie Vatler. Though suspicious, he and Yukina decide to open it, and discovers a girl inside. They later identify her as Celesta Ciate.

The 4th Primogenitor on the run

Kojou's father, Gajou Akatsuki, returns suddenly and brings Nagisa to mainland Japan for undisclosed reasons. As the days pass, he becomes more concerned about her, and even more so when a corrupted image of a magic circle is sent to his phone.

Knight of Sinful God


Despite being laid back, he has repeatedly shown to be very intelligent, clever and a quick learner; although these traits are not usually shown because he usually tends to charge without thinking, but he can be impressively logical, observational, deductive & tactical. These traits make him an excellent leader.

Enhanced Vampiric Abilities: He possesses supernatural strength, durability, agility, awareness, speed, senses, regeneration capabilities, pheromones, endurance and immortality. Being the Fourth Primogenitor, his incredible powers are far above that of most vampires. Kojou is absolutely immortal meaning he doesn't age or get sick and he will rapidly recover from any damage he receives, even from decaptation or complete incineration.

Familiar Summoning: Kojou has twelve familiars which are manifestations of his vampire's powers. Initially, these familiars would not fully obey Kojou and would often go on rampage. This is due to the fact that he refuses to drink human blood and thus, they would not acknowledge him as their master. However, he is able to control his familiars and summon them properly once he drinks blood. It is revealed that Kojou is still lacking three familiars inside him, one of them is the 12th that lies inside Nagisa while the 6th and 10th still have their Kaleid Blood bodies. They are currently in Oceanus Grave II under the custody of Dimitrie. Every time Kojou releases new familiar, he says the following chant:

I, Akatsuki Kojou, successor to the blood of "Kaleid Blood", now release your constraints. Come ....(number and name of familiar)

カレイドブラッド"の血脈を継ぎし者暁古城が汝の枷を解き放つ疾く在れ ...(number and name of familiar)

"Kareidoburaddo" no ketsumyaku o tsugishi mono, Akatsuki Kojō ga, nanji no kase o tokihanatsu. kyagare ... (number and name of familiar)

Name Description Image
1st Familiar - Aries

Prote - Mesarthim-Adamas / The Divine Sheep of Adamantine

The medium for this familiar is Kanon. It is a sheep with more than ten thousand diamonds covering it's entire body. This familiar is capable to manipulate diamonds. It is able to spread or scatter them like shotguns and form shields reflecting various attacks/abilities making it well balanced on offense and defense. The diamonds are strong enough to block Al-Meissa-Mercury's dimension eating capabilities.
Screenshot 1
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2nd Familiar - Taurus

Deutera - Cor Tauri-Sucinum / The Ox Headed King Of Amber

Ox-headed God of Amber whose body is composed of lava. It has a body of larger than 10 meters in height and carries an even larger gigantic battleaxe. It differs from other Magic-composed familiars and attacks purely with physical powers. Medium for this familiar is Grenda.
Screenshot 1-0
3rd Familiar - Gemini

Tritos - Al-Meissa-Mercury / The Serpentine Dragon of Mercury

This is the third familiar shown in the series. Kojou took control of it after drinking both Yukina's and La Folia's blood. It is a double-headed serpent dragon that is also called the Dimension Eater. This familiar is capable of reality warping / eating void and space. It is able to withstand angelic powers. It's mouth can devour anything that acts like a black hole.

Al Meissa Mercury A

Al Meissa Mercury

4th Familiar - Cancer

Tetartos - Natra-Cinereus / The Carapace of Silver Mist

The medium for this familiar is Sayaka and Yuuma. It is a silver crayfish with blue flames on it's claws. This familiar is capable to render anything ethereal by producing mists. Due to the fourth primogenitor's strength, the mists are able to cover the whole island without any difficulties. In episode 19, it is said that this familiar was only half-materialized as a wound on Kojou's chest (when Himeragi stabbed Kojou). The mists are strong enough to ward off reality warping. Natra Cinereus A
5th Familiar - Leo

Pemptos - Regulus-Aurum / The Lion of Gold

This is the first familiar shown in the series and is commonly used by Kojou. Kojou took control of it after he drank Yukina's blood. It is a lion-like familiar having glowing red eyes and has a lightning-like mane. This familiar is capable to produce and manipulate lightning. Kojou is able to manipulate the lightning to create a force field around him. The lightning is strong enough to weaken a divine vibration barrier. It can obliterate several hundreds of kilometers by just releasing it's powers.
6th Familiar - Virgo

Hektos - Minelauva Iris / Rainbow Flames of the Dark Princess

The War Maiden (Valkyrie) that holds the rainbow-colored sword of light. Manipulates laws of nature and also carries the cause and effect cutting ability. It was entrusted to Yukina and in the battle against Vatler, it was transferred to him through blood. No Image Available 2
7th Familiar - Libra

Hebdomos - Kiffa-Ater / The Black Sword of Abraded Night

The medium for this familiar is Yukina and Sayaka. It is an intelligent-type weapon, a gigantic demon sword over 100 meters in length. This trident-like sword is capable to manipulate gravity. It can obliterate few dozens of kilometers if swung from a high altitude.
8th Familiar - Scorpio

Ogdoos - Shaula - Viola / Purple Scorpion-Tiger

The medium for this familiar is Asagi. It is a man-eating tiger that is wrapped up in purple flames. It can manipulate poison and can make antidotes, as well as steal the magical power of other familiars. No Image Available 2
9th Familiar - Sagittarius

Enatos - Al-Nasl-Minium / The Bicorn of Deep Crimson

This is the second familiar shown in the series. Kojou took control of it after he drank Sayaka's blood. It is a bicorn-like familiar having glowing purple eyes, black-colored skin, purple fire-like mane and has glowing plate-shaped armor floating around its neck. This familiar is capable to produce and manipulate sound. It is able to create sound quake and waves. It can tear molecules at an atomic scale by emitting high-frequency vibrations from it's entire body.

Al Nasl Minium A

Al Nasl Minium

10th Familiar - Capricornus

Dekatos - Dabih-Crystallus / The Goat of Glinting Eyes

The whole body is covered with silver crystal scales. It has the form of Ichthyosaur with one crystal horn that resembles that of a goat's. It rules the charm, and has the ability to dominate minds. It demonstrated a power that was strong enough to dominate Kojou's other familiars when it was used in December. Medium for this familiar is Yukina and Yuiri. No Image Available 2
11th Familiar - Aquarius

Hendekatos - Sadalmelik-Albus / The Water Spirit of White Steel

Avrora awakened this familiar by force while in Nagisa's body and subsided by, then gained control of it after drinking Yukina's blood. It is a combination of an undine and a snake. This familiar is capable to revert phenomenon to it's original state which is nothingness. Due to this ability, Kojou is able to recover from any kind of injury including decapitation as shown in the series. It is able to erase conceptual existence.

Sadalmelik Albus A

Sadalmelik Albus

12th Familiar - Pisces

Dodekatos / Alrescha-Glacies / The Bewitching Princess of Azure Ice

It is a combination of a siren and a mermaid. This familiar is capable of decreasing temperature to below absolute zero, which was first seen with his sister Nagisa, who has a part of Avrora currently living inside her.


  • Kojou's hair was originally colored black, but was later changed to gray.
  • All of Kojou's familiars have names inspired from constellations.

Start a Discussion Discussions about Kojou Akatsuki

  • Can and/or will Kojou Akatsuki die?

    7 messages
    • Maybe somthing happened to him and a part of him died but not physically IDK I am really confused as well
    • He can die much like the way he consumed Avrora and though a ritual to become the fourth primogenitor. However, under normal circumstances...
  • Familiars

    4 messages
    • Question? Some progenitors have several familiars does this mean you can gain more?
    • I would more believe that the familars of the fourth progenitor are representations of the powers of vampires, say Natra Cinereus represent...