Yokai are beings from the old legends, from folktales handed down through generations. They are the beings your grandmother warns you about, when you go out at twilight. There is no direct English translation — they are at once spirits, monsters, demons, ghosts and gods.
Perhaps the most universal thing you can say about them is that they exist on the boundaries: the boundary between day and the night, the boundary between good and evil and the boundary between life and death.
