The Ao Oni (Japanese for Blue Demon) is a demon from the game Ao Oni. He is a lavender-skinned humanoid creature with a large distorted head that vaguely resembles a human. He sports large, glassy eyes, black hair, a bent nose, and a tiny, featureless body. He always has the same bemused expression on his face. In version 5.2 of the game, you can see the that the Oni has a set of sharp, fanged teeth as well as a pair of tusks in its usually-closed mouth. It possesses the ability to shapeshift and turn people into more Onis. The Onis created by this look similar to the original, except they have hair exactly like what they had when they were human. In Japanese legend, there are two kinds of onis: bad, which spread disease and famine, and good, which protect people from the bad onis. Ao Oni is also on MUGEN in "The None's Giygas's traps" as he kills another player prior to a K.O.
Aside from the Ao Oni and those it transforms, there are a number of strange Onis. Each resembles a different version of the original and are locked in a cage in what is known as the Oni Room. These are the:
- Blockman Oni - This is a square-shaped oni that moves quicker than the regular Ao Oni. When it spots its victim, it pauses for a moment then charges at it with abnormal speed.
- Hunchback Oni - The Hunchback Oni is a normal oni, though its back is hunched over, with sharper teeth.
- Hulk Oni - This oni is a large, muscled oni that bangs the floor for no apparent reason. It also is sometimes referred to as "Squato". Because of its size, it moves slowly in most cases. It is the largest of the onis.
- Deformed Oni - This oni resembles the regular Oni, though the oni itself is completely warped, hence the name.
- Blob Oni - Also known as the "Eye-see Oni", this oni is irregular. It looks like an amorphous mass with many eyes on it. The Blob Oni is relatively slow and sluggish.
- Encephalo Oni - This oni mutation is the head of the regular oni but lacks a mouth and has many tentacles. It bears resemblance to a jellyfish.
- Caterpillar Oni - This oni is also a sluggish type of Oni. It looks like a caterpillar with its head up. It has 5 eyes on each side and many, tiny legs.
- Flying Oni - This oni has spike-like protrusions from its head and floats back and forth without any other movement, Its nickname is called "Niji Oni"
- Clock Oni - The oni resembles a clock with thorns, as if exploding, or a stalactite. It levitates while staying affixed to its position, one of the thorns stretching and shrinking continuously. It seems to be the flying oni looking straight ahead.
- Tall Oni - A regular oni, only taller. He's still just as dangerous
- Toothed Oni - This oni is similar to the original, but with its mouth open, revealing its teeth and tusks. It is also wide-eyed as opposed to its right eye being squinted slightly.