Kojo was a normal high school student 3 months prior to the beginning of the story, until becoming the 4th progenitor after his predecessor, Avrora Florestina inserted her spirit into him because of a wish. He claims to remember nothing of the incident. When he's aroused, his blood lust takes over and the only way to stop it is to drink his own blood, usually from the nosebleed he gets. As a vampire, Kojo possesses superhuman strength, speed, reflexes, and durability, but is much more powerful than normal vampires due to his status. He has also inherited Avrora's twelve familiars. Due to never having drank human blood, Kojo at first has no control over his powerful familiars, but after drinking Yukina's blood, they acknowledge him as their master. By drinking the blood of others who have familiars, he is able to gain control over their familiar.