Oni’s are a form of Yokai which is the Japanese word for Demon/Devil, they are a humanoid like figure and can be distinguished by their odd number of body parts or wild colouring in their skin.
The Oni’s originate from Japanese Folklore, the word “oni” is speculated to be derived from the word on meaning hide or conceal, this links to the belief that oni’s are originally invisible spirits that cause disasters, disease and other unpleasant things to amuse themselves. Eventually Oni’s will want to take form, they can turn into anything they can think of which will allow them to deceive humans which will also allow them to devour the humans a lot easier because the humans won’t expect it.
Oni’s have the power to inflict diseases to anyone they see fit, they can also cause any number of natural or unnatural disasters wherever they want and they can do anything they want that can cause harm to anyone sometimes acting like a poltergeist. They enjoy deceiving humans and then once they have played with their food they decide to devour them whole.