In the Vampire Yukierre AU, discussions between @yuki-shipnoda and I went to some fun rabbit holes.
More specifically how would a Japanese vampire arise given the amalgamation of Shinto, Buddhist and Confucian beliefs.
What we've come up with is that the Japanese vampire or known colloquially as the kyuuketsuki isn't made with a typical bite from another vampire.
Kyuuketsuki are born when a dead body doesn't receive the proper purification rites before they are interred or aren't cremated (though a few kyuuketsuki were powerful enough to reassemble their bodies from the ashes and bone fragments). If the person met a sudden and brutal end, they are more likely to end up a kyuuketsuki.
They would have the shapeshifting powers, enhanced senses,an immense healing factor (if provided with enough blood) and would retain animal like behaviors in their human forms and kyuuketsuki are the only beings that illusion magic from other yokai such as kitsune and tanuki will not work on. They can also walk in direct daylight (as a direct middle finger to Amaterasu), in stark comparison to their Western counterparts.
Kyuuketsuki prefer the forms of birds rather than the typical wolves, bats and rats of Western vampires, finding them more useful with feigned frailty and innocence to lure their prey. Songbirds are the most common form for kyuuketsuki to take, though larger birds like crows and ravens, parrots, and even birds of prey are noted but uncommon. Their scent can even mimic the animals they shift into and often fool typical animal populations to more easily blend in.
But they do share some weaknesses with the Western vampire: holy water from a Shinto priest/miko, blessed salt used in Shinto purification rituals, Shinto/Buddhist prayers, they are unable to enter holy spaces, must be invited into buildings, silver can be used against them (vintage photography (Ex. Polaroids) will not show kyuuketsuki/vampires, old mirrors backed with silver will not show their reflections, and direct contact with silver burns and repels them).
Kyuuketsuki also have subtle tells that children are more likely to pick up on: their fangs will be seen in smiles both small and big, their laughter would be closer to their preferred animal form call rather than a human laugh, cool pallid skin , sharp nails that resemble talons, eyes that flicker red in both human and animal forms and upon scenting blood.
Japanese vampires can also intake both human blood and animal blood to satiate their neverending thirst. They use both animal and human forms depending on which prey their animal form prefers though larger prey can be hunted with groups of kyuuketsuki. Blood is the only thing a kyuuketsuki is filled due to the degenerated organs in their body, but other fluids like alcohol or tea can also be drunk to better keep up the facade of being human.