Character setting information
The world where Kyou comes from is more or less just as ours is now, only with two differences. The first is that technology is slightly more advanced; maybe 5 or so years ahead of today's. The second is vampires. Both they and humans have been living with the knowledge of the others existence for almost as long as history has been recorded; however, the cooperation between the two is still a fairly new concept, having begun only a few centuries ago.
The average human in this world knows about vampires, and the majority are accepting of them. While there are some who don't even interact with each other, others will take part in relationships, be it friendships, on the job, neighbors, etc. There are also some who find romance with the other, but inter-species romances and marriages aren't all that common. In fact, the latter has caused problems amongst the families involved, with the children of the couple being prone to teasing by their peers. In some cases, families have been torn apart.
For the most part, there are two 'types' of vampires. Full-blooded, and the more uncommon, half-breeds. Their existence is the result of an extra chromosome. A half-breed can come about in two ways: the first is the most obvious way, which is when a full-blood decides to 'turn' a human, by biting them and then having the human drink the vampire's blood in return. The second way isn't seen as often, but it's how Kyou became a vampire, and that's by blood transfusion. The only way for a full-blooded vampire to come into existence is to be born as such, be it from a vampire couple, or a vampire/human pair, seeing how the genetic make-up of a vampire is more dominant than that of a human.
There are a few differences between a full and a half vampire. The primary one is the fact that the aforementioned absolutely must consume blood in order survive, be it from a human or animal; while some will eat regular, human food as an indulgence and for the taste, their bodies are incapable of retaining the nutrients within said food. For the half-breeds, this ability is a part of them that remained human; however, they still must take in blood for energy. While a full-blooded vampire will typically need to feed at least once every other day, the half-breeds are able to go for a short while. Two weeks or so tends to be the average
Physical injuries and death can fall upon both vampires and half-breeds, although those who are full-blooded are able to withstand more. Death typically happens by extreme means, with heavy blood loss supposedly being the most common. Also, because halves age a bit slower than humans (though far from as slow as full-blooded vampires do) dying from old age is also possible. Additional differences include fang size, body temperature, and general speed/agility/strength. For a half-breed, their fangs are about a half of the size of full-blooded vampires. The natural body temperature of a half-breed is less than one degree cooler than that of a human, while full-blooded vampires are noticeably more chilled to the touch; both have a slower resting pulse-rate. Although the strength, agility, and speed of a half-breed isn't particularly extraordinary, or quite as remarkable as a full vampire, it is noticeably more than that of an average, healthy human.
Even more recent than the cooperation between the two species are the laws that ban vampires from hunting humans, be it for food or otherwise, and vice-versa for humans. Murder and assault, no matter what species the actions are between, have consequences.
What is allowed, however, is blood donation. The rise of blood centers specifically for vampires have increased over the past fifty or so years, primarily as a way to further encourage the coexistence between the two species. Normal blood banks and blood donation for medical purposes are kept and run separately. There are also those humans who consent to being fed from directly. Although this practice more common as an intimate act between both vampire and vampire/human couples, there are still those who do so anyway.