The mythology of Japan has a long history dating back more than 2,000 years. It became part of two major religious traditions: Shinto, an indigenous religion, and Buddhism, which developed in India and came to Japan from China and Korea.
Sources
For many centuries myths were transmitted orally in Japan.
1) KamaitachiKamaitachi, literally means "sickle weasel." There are three of them, sometimes brothers, sometimes triplets, who go around cutting off people's legs. The first weasel knocks someone down, the second cuts off the legs, and the third sews up the wounds. They move so fast basically people blink and then suddenly realize they no longer have legs. Admittedly, the fact that one of the weasels takes the time to patch people up before absconding with their limbs helps. But, if the idea that you could suddenly discover that weasels have stolen your legs doesn't scare you, then you're a better man than I.
2) Joro-GumoThe Joro-gumo is a spider-woman, but she's not a member of the Avengers with a needlessly complicated backstory. She's a giant spider, with the ability to take the form of a beautiful lady (sometimes the top half is human, and her lower torso is that of a spider) who seduces men, wraps them up in her webs, poisons them, and eats them. One variation of the Joro-gumo myth says that sometimes she appears as a woman holding a baby, who asks men passing by to hold it. When they do, they are someone surprised to discover the "baby" is made up of thousands of spider-eggs, which burst open.
3) Teke TekeTeke Teke is more of an urban legend than a regular myth, as it's reasonably new. She's the spirit of a girl who tripped on some train tracks and was cut in half by an oncoming train. Now she crawls around looking for other people to share her fate, which she facilitates by cutting them in half with a scythe. There's a variant of the Teke Teke myth about a girl named Reiko Kashima, who was also cut in half by a train; now she wanders bathroom stalls and asks people on the toilet if they know where her legs are. If people don't answer with "The Meishin Railway," she cuts off their legs, which is bad at the best of times, let alone when you're trying to poop.
4) GashadokuroThis spirit is pretty simple — it's a giant skeleton made of of the bones of people who have died from starvation. They wander around, grab you, and bite your head off, drink your blood, and add your skeleton to the pile.
5) KatakirauwaThe ghosts of baby pigs which 1) have one ear 2) cast no shadow and 3) steal your fucking soul if they manage to run between your legs. I think I'd rather be chased by the giant mass skeleton that a bunch of tiny squealing dead baby pigs, thank you.
6) Aka MantoAnother one of the many, many Japanese ghosts that murder people while they're trying to take a shit, Aka Manto approaches people in bathroom stalls and asks them a simple, if perplexing question: "Would you like red paper or blue paper?" If you say red, your flesh is sliced into ribbons until you're effectively red. If you choose blue, you're strangled to death. If you pick any other color, you're dragged to hell. There's a variant who asks if you want a red or blue cape instead of paper; choose red and the skin is flayed off your back, choose blue and all the blood is drained from your body. The point is never go to the bathroom in Japan.
7) TsuchigumoGreek mythology is known for its variety of mixed-up monsters — e.g. the manticore, which has a lion's body, bat wings, and a human head — but they have nothing on Japan. Meet the Tsuchigumo, creatures with the body of a tiger, limbs of a spider, and the face of a demon. They eat unwary travelers (actually, they eat wary ones as well, I'm sure). Once a powerful Japanese warrior killed a Tsuchigumo and 1,990 skulls fell out of his belly. That's a monster who is frighteningly good at his job.
8) KekkaiChildbirth seems difficult enough before you bring in the possibility that you may give birth to some kind of demon/monster/thing. In Japan, these are called Sankei, and the worst of them is the Kekkai. Basically, instead of giving birth to a baby, a lady gives birth to a lump of flesh and blood and hair, when immediately runs off, straight out of the vagina, and tries to burrow underneath its mother's home in order to murder her later. No wonder Japan's birth rate is declining.
9) OshiroibabaOne of the many, many horrible demon women that apparently wander around the nation unfettered, Oshirobaba is an old crone that goes around asking girls if they'd like to try some of her face powder, like the world's creepiest Avon lady. Taking make-up from strangers is bad idea in general, and taking it from old ladies is even dumber, because the Oshirobaba's powder makes your face fall off.
10) Ittan-MomenThe Ittan-Momen doesn't sound particularly scary; it's basically a sentient roll of cotton that just flies around in the wind at night, wandering around. But the Ittan-Momen is also a sadistic asshole, because if it sees you, it will either wraps itself around your neck and choke you to death, or wrap itself around your head and suffocate you. Again, the idea that you can be walking back from the convenience store and suddenly get murdered by a large piece of cloths is deeply disconcerting to me.
