Kojou Akatsuki

is the male protagonist of the light novel series, Strike the Blood. 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.

He is voiced by Yoshimasa Hosoya in the anime adaptation of Strike the Blood.

Background
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 used 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.

When Kojou was in middle school, he participated in his school's basketball club and seemed to have performed very well, winning a city championship and Most Valuable Player. However, Kojou's skills were so high that it became nearly impossible for his other teammates to keep up with him and eventually gave up, leaving it to Kojou to win the games for them. During one game, Kojou was trying to score a point when one of his opponents attempted to stop him with a foul. As a result, both Kojou and the opposing player were injured. This forced Kojou off the gym for the rest of the game, which meant his teammates would have to be relied on. But because they were so dependent on Kojou, all they did was just let the other team win. Kojou was so shaken by this incident that, shortly after, he quit the basketball club. Even though he isn't part of the club anymore, he is still sometimes shown playing basketball in the light novels and anime.

Appearance
Kojou is a handsome 16 year old boy. 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.

Personality
Kojou is a kind, empathetic person, who goes out of his way to help others. He is also an intelligent, sly and carefree individual. Underneath his relaxed demeanor, however, Kojou has a quick temper which is frequently triggered when he's made fun of or talked poorly about by other characters. Kojou also has a very serious side of him which becomes more and more apparent as the series progresses. When angered, Kojou becomes a quite fearsome adversary. Kojou has indomitable willpower and a 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.

Abilities
Kojou is a vampire, the fourth primogenitor, as such he gains several abilities


 * Cleansing: A phenomenon that alters the laws of physics and magic, fundamentally allowing its user to warp reality.
 * Enhanced Vampiric Abilities: Supernatural strength, consciousness, durability, speed, agility, regenerative abilities, endurance, senses, pheromones and immortality.
 * As Kojou is immortal, he cannot become old or sick and will recover from any damage he receives.
 * Familiar Summoning: Kojou can summon twelve familiars, that act as manifestation of his vampiric powers. He gained control over them by drinking human blood.
 * 1st Familiar: Mesarthim Adamas - This familiar is able to manipulate diamonds. It is able to disperse or scatter them like shotguns and form shields that reflect various attacks and abilities, which makes it well balanced in attack and defense.
 * 2nd Familiar: Cor Tauri Sucinum - This familiar can manipulate both lava and tectonic plates, but it mainly attacks in close quarters.
 * 3rd Familiar: Al-Meissa Mercury - This familiar is capable of eating space itself along with the dimension. It is able to destroy Angel-Faux Divine Oscillation barrier. This is one of Kojou's most dangerous familiars as it can even leave severed space after it's attack which may pose danger for third parties.
 * 4th Familiar: Natra-Cinereus - 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.
 * 5th Familiar: Regulus Aurum - This familiar is capable of producing and manipulating electromagnetic energy. Kojou can manipulate the beam to create a force field around him. The ray is strong enough to destroy a barrier of divine oscillation and neutralize Wiseman's Blood energy beam, which was already capable of atomic-level destruction.
 * 6th Familiar: Minelauva Iris - This familiar is capable of manipulating the laws of nature and also carries the cause and effect cutting ability.
 * 7th Familiar: Kiffa Ater - This familiar is an intelligent-type weapon, a gigantic demon sword over 100 meters in length. This trident-like sword is capable of manipulating gravity. It can obliterate a few dozens of kilometers if swung from a high altitude.
 * 8th Familiar: Shaula Viola - This familiar can manipulate poison and can make antidotes, as well as steal the magical power from other familiars.
 * 9th Familiar: Al-Nasl Minium - This familiar is capable of producing and manipulating sound. It is able to create sound quakes and waves. It can tear molecules at an atomic scale by emitting high-frequency vibrations from it's entire body.
 * 10th Familiar: Dabih Crystallus - This familiar's ability is mental and spiritual manipulation.
 * 11th Familiar: Sadalmelik-Ablus - This familiar is capable to revert phenomenon to its 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.
 * 12th Familiar: Alrescha Glacies - This familiar can manipulate water and lower the temperature below absolute zero.

Trivia

 * Kojou appears as an assist character in Dengeki Bunko: Fighting Climax.
 * Kojou appears as a main character in Dengeki Bunko: Crossing Void.
 * All of Kojou's familiars have names inspired from constellations.
 * Kojou is voiced by Yoshimasa Hosoya in the anime adaptation of Strike The Blood.
 * He shares a voice actor with: Tamaki Katagiri (Black Bullet), Jin Asukai (Boogiepop and Others (2019)) and Sladder Honeysuckle (Heavy Object).