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Oni (鬼, literally translated as Demon): Hideous giants with sharp claws, long horns and wild untamed hair. Generally humanoid but occasionally they are shown with odd numbers of eyes or extra fingers and toes. Their skin color is usually red, blue, black, pink, or green. Oni typically wear tiger skins and carry fearsome iron clubs called kanabō (金棒). In the earliest legends, oni were benevolent creatures who fought off evil and malevolent spirits.
Kappa (河童, literally translated as River Child): A water-based demon with webbed hands and feet, a turtle shell, and a circular dish on top of its head. It can exist out of water only as long as the dish contains water. About the size of a small child, the Kappa is very strong. It attacks horses, cattle, and humans, dragging its prey into the water, feeds on their blood, or drains their life force, (etc.) leaving nothing behind except a hollow gourd. It is said to sometimes drag unwary travelers into the water and drown them. In many localities, drowning is still referred to as GAPPADOKO. When benevolent, the Kappa is supposedly a skilled teacher in the art of bone setting and other medical skills. The Kappa is always portrayed as trustworthy despite its many evil ways. When captured and forced to promise never again to harm anyone, the kappa always keeps its promise.
Kitsune (狐, literally translated as Fox): A fox apparition, and one of the HENGE (Shape-Shifters). The Kitsune most often appears as a woman to human men or as a man to human women. Often wishes to merely play pranks, but sometimes desires to mate with humans. They are generally considered harmless. The Japanese people believed that the kitsune was the messenger of the Fox goddess Inari.
Shikigami (式神, literally translated as Formula God): Spirits that are summoned to serve or protect an Onmyoji, much like the European wizard's familiar. Shinto priests and some miko also are capable of summoning shikigami. Shikigami can appear as birds, small animals, or humans. The range of abilities possessed by a shikigami is dependent on the Onmyoji's capabilities.
Tanuki (狸, literally translated as Raccoon-Dog): A raccoon-dog apparition and one of the HENGE (Shape Shifters). The Tanuki is fond of drink and food to excess, often trick humans by purchasing sake with leaves disguised as money. Tanuki are generally harmless tricksters - but their tricks seem to escalate if the one being tricked merits it. There is a legend about tanuki in Japan, concerning the origins of Inu-yama (Inu mountain) in Gifu prefecture, which was the home of Oda Nobunaga in 1575.
Tengu (天狗, literally translated as Heavenly Dog): One of the HENGE (Shape Shifters). a long-nosed mountain and forest spirit with a beak and wings; part bird, part man, some were said to mimic mountain priests (yamabushi)- these were portrayed as being more mischievous than evil and were often depicted helping people. Others were said to always be trying to snag an unwary traveler or plump monk to eat. Their main abilities are the ability to speak to humans without moving their mouth, the magic of moving instantly from place to place without using their wings, and the sorcery to appear uninvited in the dreams of the living.
Inugami (犬神, literally meaning Dog God): A demonic race of creatures that resemble dogs with ability to shapeshift from dog to human form.
↑Note: the term yōkai covers a wide rage of creatures, and has no true cognate in English. An English cognate would need be a word that would cover elves, dwarves, succubi, nymphs, etc. As no such word exists, "demon" is commonly used in the English dub.