A Half-vampire is the result of a union between a vampire and a human. Yuriya Tachibana and Kanon Usui are the only named half-vampires in the story, but according to Elda, there have been several others.
In the past, there has been rare instances of love between humans and vampires. As a result, their offspring were born human-vampire hybrids. However, due to a defect of their vampire genes, half-vampires are born sterile. Elda Marker thinks the human genetics are to blame, but it's more likely due to the vampire side; every 1000 years or so, vampires start losing the ability to reproduce and must drink the blood from the Psyche to restore fertility in their descendants. This causes the parents anguish, as they feel horrible for dooming their children to such a fate.
One half-vampire grew resentful of its heritage and lead a church to attack all the vampires in Europe, resulting in many migrating to Japan. As a result, half-vampires are hated for simply existing. Brigitte Braunlich has openly told Yuriya to die and called her a soulless doll. Elda nearly killed Yuriya because she remembered the betrayal 200 years ago. However, others such as Glark (Yuriya's uncle), Karin and Kenta don't view them negatively.
Much like a normal vampire, half-vampires live like normal humans until they reach 13 years of age. Unless their parents tell them of their heritage, half-vampires will assume they are human. Unlike true vampires, they have no control over their instinct to feed on blood; so when they awaken, they will bite the nearest person they can. Once they drink blood, a half-vampire will need to stay out of the sunlight for 24 hours; afterwards, they can resume living like a human. According to Yuriya, these "attacks" happen once a month.
Daywalking: As they are half-human, hybrids can go about life like humans. However, once they feed monthly, they are forced to stay out of the sun or get sunburned badly.
Bat detection: As Yuriya demonstrated, she can tell when the vampire familiars are around; she can even touch them and pull off a wing.
Memory erasure: Hybrids have the ability to erase the memories of people they bite. However, unless they have training, they are unskilled.
Fully vampiric once a month: Once a month, a hybrid must drink blood; their vampire instincts are too strong for them to resist.
Sterile: Due to their genetic origins, hybrids are unable to reproduce.
The human-vampire couples that had children
Kenta Usui (human) and Karin Maaka (vampire) Edit
The main couple of the story. They love each other dearly, despite the obstacles involved.
Ms. Tachibana (human) and Yuriya's father (vampire) Edit
Their relationship is not known well, but the vampire father was only able to visit Ms. Tachibana and Yuriya twice a year.
- Kanon has the extra ability to become adored by anyone she meets, thanks to being Sophia's current reincarnation.
- Hybrids retain their sense of taste, like Psyche do.