Most Popular Japanese Demons
There are so many different types of yokai (English name would be demons) in Japan, in fact Japanese mythology has yokai ranging from deadly, to benign or outright strange.
The most popular yokai are the Tengu, Kappa, Kitsune, Tanuki, and the Oni.
Tengu were originally seen as bad omens, evil, and war mongers. Now, however, they are revered and respected as a demi-god of the mountains.
They are considered as both a religious deity and a yokai, Tengu are described as having the figure of human males (usually), with red skin, long noses, and they wear a small black hat and white robes.
Before the Tengu became idols of worship and good, they were rather mischievous; kidnapping women, stealing, creating false visions of buddha. It was believed that Tengu were the fallen spirits of monks, priests and nuns that died.
Although, their reputation took a turn eventually, they became guardians of mountains, and around the 1400's they began training warriors in martial arts. With their newly found good nature, they no longer played tricks on people, as much. This means they went from being the trickster to tricked, that even a child could easily fool them.
I've already written an in depth hub about Kappa, but basically they are dwarf sized water imps, they are devious, and will easily kill you for your flesh. However, they can also be easily tamed.
They resemble old men, and have green skin, scales, and a tortoise shell on their back.
Kappa may be devious flesh eaters, but once you beat them in a bet or if they make a promise with you, they'll become loyal friends.
Aw, isn't it so cute... when it's not sucking your entrails out!
Yes, kitsune is my favorite...
Kitsune which translates to "fox" are nine-tailed foxes, yes, yes, we've all seen Naruto. Don't get too excited though, the kitsune from Naruto isn't exactly as accurate to folklore as you think.
Now, I mentioned that a kitsune has nine tails, however, that depends on it's power, wisdom, and age, basically once a kitsune gets it's ninth tail, it is at the peak of it's power. A kitsune looks like any other fox, except it may have any number of tails, unless it has the ninth tail then it will have gold or white fur.
Kitsune are not ghosts or spirits of something that has died, they are their own species. Unlike the nine tailed demon from Naruto, they aren't particularly evil, and though they may be strong, they aren't insanely OP like in the anime. Kitsune are actually shapeshifters, but for the first 100 years of their life they will be in the form of a fox, once they reach the 100th year, they can then shape shift into humans, usually females, but that doesn't say anything about their real gender, kitsune can be either male or female.
Rather than strength kitsune are seen as incredibly intelligent and wise. a nine-tailed kitsune will be able to see or hear anything from anywhere in the world, or have infinite knowledge, or even become omniscient.
Okay, when I said they weren't OP I lied a little bit.
Kitsune love their freedom, so if you start bossing one around get ready for a world of hurt, if you ever need to kill one (please don't, they are so uber cool) simply cut off it's tails. Or if you want to find out if a person is actually a kitsune in disguise, simply get it drunk, they are horrible at hiding their tails, especially when drunk.
They are also terrified of dogs, I guess we all have our phobias... Even omniscient beings.
The Tanuki is actually also a real animal, it translates to "raccoon dog" and you can find them in Japan.
Tanuki is a jolly, happy-go-lucky yokai, and like the kitsune it can shape shift as well. It wasn't always so friendly though, like the tengu they were considered evil and malicious, but that image quickly changed to a raccoon that wears a straw hat, carries a flask of alcohol, with a huge round belly, and very very large... genitalia. They are now an icon of prosperity, and many restaurants will use tanuki statues to greet and welcome customers.
Oni are the ogres of Japan, they too have a humanoid shape, but are many times taller than the average human, they have horns, red or blue skin, long, messy black hair. They wear lion cloths and wield iron clubs
Out of all the yokai in this list, they are the most ferocious, they come straight from hell. It is believed that evil humans that end up in hell are transformed into oni, and become the servants of the devil otherwise known as Lord Enma in Japan. They cause disasters, punish the damned and spread disease.
The oni that are the most dangerous to us are the humans that are so beyond redemption they transform right on Earth. Forever stuck here to wreak havoc on us.
The term oni was actually coined for all demons, but now they refer to a specific category.
In anime, oni are not always portrayed as bad, this can be a teensy tiny bit misleading, especially if you expected to become friends with them after watching Natsume Yuujinchou