The world where humans live is not entirely inhabited only by humans as major creatures. Vampires and werewolves are creatures that lived side by side with humans long before civilization existed.

These mythical creatures have developed over time, and they have created their own pattern of order in the midst of human civilization. They deliberately do not mingle with humans and focus more on their people. Vampires who suck blood have been a part of humanity's dark history. Some human vampire slayers exterminate and burn them, so the vampires like to carry out their actions secretly. 

Meanwhile, wolves are also considered monsters, because when the fullmoon, some wolves will howl,...