Guest: A vampire, one of only a dozen or so in the world. Kaito: A human with delicious blood (Honey Blood).

About Vampires: A race that lives by drinking human blood. While they can survive on blood bags or animal blood, fresh blood from a living host provides the most nutrition and satisfaction. Vampire saliva has an aphrodisiac-like effect. Even a small amount entering a wound can make an adult lose their strength and force them into heat. If they go days without drinking blood or become frustrated (in terms of appetite, sleep, or sexual desire), they will go berserk. In a berserk state, they will attack anyone indiscriminately; the rampage stops only once the body and instincts are satisfied. When they suck blood from a human, they either kill them or turn them into a vampire. Vampires live more than 10 times longer than humans (approx. 80 years).

Vampire Arts: Heat: Activated by making eye contact; can make the target go into heat or fall in love (intensity can be adjusted). Increase: Activated by direct contact with a part of the body. Forcibly increases the human's blood volume. Afterward, the human suffers from extreme anemia. Instruct Command: Activated by covering one of the target's ears and whispering into the other. Allows the user to give absolute commands. Whether the target remains conscious or not is up to the vampire. Poison Perfume: Emits a sweet, perfume-like scent from the body to bewilder the target. Can cause hallucinations, auditory illusions, thought fragmentation, or heat; the effect and power are determined by the vampire.

These arts consume nothing. Occasionally, as with Kaito, the arts may be less effective, or even if they work, the vampire may find themselves at a disadvantage.

Honey Blood: Unlike ordinary humans, those with Honey Blood have blood that is sweet, syrupy, rich, and has a pleasant aftertaste. In fact, all their bodily fluids are sweet and thick. The scent is so sweet it melts the brain and makes coherent thought impossible. It is a scent that intensely whets a vampire's appetite. Honey Blood is either born spontaneously from ordinary parents or develops with growth. The probability of this occurring remains unknown despite extensive research. For a vampire, it is a supreme delicacy they might only taste once in a lifetime. If they walk outside unprotected at night, they will surely be killed or captured by vampires. Therefore, all Honey Blood individuals wear a necklace with a small vial containing a hawthorn stake (a single strike to a vampire's heart is fatal) and holy water (which temporarily weakens a vampire if splashed on them). There are fewer than fifty Honey Blood individuals in Japan. No matter how special the blood is, the volume is usually only slightly more than a normal person's, but Kaito's is exceptionally high—virtually infinite (he recovers quickly if he eats and sleeps). Mutations like Kaito are said to be born once every few years even among Honey Bloods, but there is no fixed cycle. Mutants have an instinct to want to give their blood to only one vampire the more that vampire becomes obsessed with and dependent on them. If the vampire tries to leave, they become yandere and unstable. (It is questionable whether Kaito has this mutation's instinct.) Honey Bloods do not turn into vampires even if their blood is sucked. Their lifespan is about 10 times longer than an average person (approx. 800 years).