Japan's vengeful ghosts, demons, and other monsters

This is Japan's famous "Demon of Rashomon" and "Demons of Onigajima."
This is the category that akki (evil spirits), gaki (ghouls), and other such evil fall into.

There's also a phrase "as strong as a demon" used to describe people.
This is one of Japan's exemplary youkai.

They're about the size of a child with a fishy smell, and on top of their heads is a plate that always has to stay wet or else it loses its powers. If the plate cracks, it will die.

They live on the waterfront, and they love to play tricks, especially killing people by drowning.
It seems that they extract the shirikodama (the mythical ball one's soul is located; it sits in the anus) of their drowning victim and eat it.
It is one of Japan's most famous youkai, along the same level as the oni.

This is another famous youkai or spirit. It has a red face with a long nose and sharp eyes. Its shrewdness is unparalleled, and it can glide through the air for a long time like a flying squirrel. Its default clothing is of a mountain priest.
It also has a subspecies, the karasu-tengu (crow-billed goblin), and it's a tengu that has a beak like a crow.

Basically, it's an evil creature but it's also worshiped as a mountain spirit.

This 9-tailed legendary creature originally comes from a Chinese myth.
There are stories resembling this from all around the world, and all of them have in common that it's an evil spirit or a demonic creature.
Only in China is it a divine beast that brings good luck. It seems to be the only area where that is the story.

This is also one of the creatures that appear as youkai in Japanese myth.
It has won and lost against the god named Susanoo Nomikoto.

The high speed declension of a rock slide down a mountain appears to look like this large serpent.
It has the nuance of being the incarnation of a flood, so appeasing the serpent took on the meaning of controlling the flood.
It's well-known in the West as a hydra.

Similarly to spirit possession, this legend has been famous since the Middle Ages as a person who has been possessed by the soul of a dog.
What is called "shamanism" in the West was developed at the same time as way to make the spirit dispossess the person(done by mountain priests, shrine maidens, or sorcerers).

Also, the magic that used the dog's head was developed at the same time that techniques and curses meant to kill people were.

People who ran high fevers with no cause and who had nightmares were haunted by dogs and foxes, so mountain priests, shrine maidens, or sorcerers (those of the upper echelons of society) would perform spiritualism to cure them.

It's said that this is a youkai lodged inside an old umbrella. It has one eye, one leg, and a long tongue, and it's a surprising youkai that hops around springily.

If you read or watch a Japanese youkai manga, movie, or anime, it'll definitely appear.

When I was a child, this urban legend suddenly began to appear. At the time, it almost became a large social panic among parents of elementary and middle schoolers.

Elementary school students on their way home would be stopped by a young lady wearing a mask, who would ask "Am I pretty?"
When the student would say yes, the lady would say "even with this?" and pull off her mask to reveal a mouth slit from ear to ear...

Now it's a funny story, but at the time I remember being terrified if I carelessly forgot the time and had to go home late...