Oni are creatures from Japanese mythology. The term Oni is equivalent to the term "demon" or "ogre", as such can describe a wide variety of entities. Onis are popular creatures from Japanese literature, art, and theater.
On the other hand, the appearance of the oni is probably derived from Chinese demons, imported from the tales of the Buddhist underworld. Emma-Daiō, the king of jigoku (hell), is sometimes imagined to have two attendants, the aka-oni (red ogre) and the ao-oni (blue or green ogre).
While in folktales the oni are usually malicious, man-eating creatures to be feared and destroyed by wandering heroes, the oni can also have a protective function. The onigawara tiles, found at t...