Japanese Mythology

Mizuguma

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Tradition / Region: Japanese Mythology
Alternative names: Water Beast of Mizushima
Category: Bear

The Myth

The Mizuguma, or Water Bear, is a mysterious black beast said to have lived in the depths beneath Mount Hakusan. It was believed to be responsible for the devastating floods that repeatedly struck the Tedori River during the 18th century.

During one of these floods, people noticed a huge black object protruding from the river. It resembled neither stone, wood, nor the body of a dead animal. Covered in black, leather-like skin, it had no visible eyes, nose, or head, only several branch-like limbs. Hoes and bamboo poles could not pierce its hide.

When a coconut floated downstream, the creature suddenly extended one of its limbs, seized the fruit, pressed it against its mouthless body, and drained the oil from within before letting the empty shell drift away. Realizing it was alive, the villagers tried to burn it with flaming straw. The fire finally split its hide, drawing black blood.

The wounded beast responded with a tremendous roar. Towering waves crashed onto the riverbanks, embankments burst apart, and floodwaters surged across the countryside. Wherever the creature rolled, deep pools formed, and the flooding continued to devastate the surrounding villages.

Unable to defeat it, the people prayed daily by reciting the Kannon Sutra for one hundred days. One night, a faint light appeared, and the black creature was seen swimming upstream toward the mountains. After its departure, the floodwaters receded, the river returned to normal, and the Water Bear was never seen again. It was thereafter believed to dwell once more in the deep abyss beneath Mount Hakusan.

Sources

TYZ. (n.d.). 水熊 (Mizuguma). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1071303462.html

Kawaguma

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Tradition / Region: Japanese Mythology
Alternative names: Kawakuma
Category: Bear

The Myth

The Kawaguma, meaning “river bear,” is an aquatic yōkai said to inhabit the deep rivers of northern Japan, particularly the Omono River in Akita Prefecture and the Shinano River in Niigata Prefecture. Covered in black hair and rarely seen by humans, it spends most of its life hidden beneath the water.

Little is known about the Kawaguma’s habits because it remains at the bottom of deep rivers. It is sometimes curious enough to approach boats, clinging to their sides or stealing objects and dragging them back to its underwater lair. It is also blamed for digging into riverbanks, causing them to collapse and bringing about floods.

One famous legend tells of a lord who was hunting from a boat on the Omono River when a black, hairy hand suddenly reached up from the depths and snatched away his rifle. A skilled diver later recovered the weapon from the deepest part of the river, and it thereafter became known as the “Kawaguma gun,” remaining a treasured possession of the Satake clan.

Another tale recounts how a ferryman had just tied up his boat for the night when he heard a splash behind him. Looking back, he saw a pair of black, hairy hands gripping the side of the boat. Startled, he struck at them with a large knife. The following morning, a severed hand was found inside the boat. It resembled the paw of a cat but was covered in black fur, and everyone who saw it declared that it belonged to a Kawaguma.

Sources

Foster, M. D. (n.d.). Kawaguma. In Yokai.com: The Illustrated Database of Japanese Folklore. Retrieved June 29, 2026, from https://yokai.com/kawaguma/.

Onikuma

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Tradition / Region: Japanese Mythology
Alternative names: Demon Bear
Category: Bear

The Myth

The Onikuma, meaning “demon bear,” is a fearsome yōkai said to originate in the mountain forests of Japan, particularly the Kiso Valley in Nagano Prefecture. It is believed that when an ordinary bear lives for many years, it transforms into an Onikuma, growing far larger than any natural bear and gaining immense supernatural strength.

Unlike ordinary bears, an Onikuma is able to walk upright on two legs. It is powerful enough to move enormous boulders that even groups of men cannot shift, and it can crush small animals with a single blow. Although it lives deep within remote mountain forests and is active mainly at night, it occasionally descends into nearby villages in search of food.

When an Onikuma enters human settlements, it is known for carrying away livestock such as horses and cattle before disappearing back into the mountains. Because of its tremendous strength, encounters with the creature are rare but often deadly, leaving villagers with little choice but to organize dangerous hunts.

Traditional accounts describe a special method for killing an Onikuma. Hunters blocked the entrance to its den with a massive wooden frame covered in wisteria vines. They then forced branches and brush through the narrow openings until the beast’s shelter became completely filled. Eventually the trapped Onikuma burst through the entrance, where hunters waited to attack it with long spears and rifles.

According to legend, several Onikuma were slain during the Kyōhō era (1716–1736). Their hides were said to be so enormous that each one could cover an area of more than six tatami mats. Large boulders scattered throughout the Kiso Valley are also known as “Onikuma stones,” as local tradition claims they were hurled down the mountainsides by these mighty demon bears. In Hokkaido, bears that attacked humans were likewise feared and referred to as Onikuma.

Sources

Foster, M. D. (n.d.). Onikuma. In Yokai.com: The Illustrated Database of Japanese Folklore. Retrieved June 29, 2026, from https://yokai.com/onikuma/.

Wikipedia contributors. (n.d.). Onikuma. In Wikipedia. Retrieved June 29, 2026, from https://en.wikipedia.org/wiki/Onikuma.

Kōmori-ba

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Tradition / Region: Japanese Mythology
Alternative names: –
Category: Bat

The Myth

The Kōmori-ba is a bat-like yōkai that appears in the eighteenth-century illustrated collection Yōkai Chakutōchō. It is depicted among a gathering of supernatural creatures alongside a red oni and a skeleton monster.

Unlike an ordinary bat, the Kōmori-ba does not have wings formed by membranes stretching between its limbs. Instead, it possesses a pair of large wings that grow directly from its back, giving it a more monstrous appearance.

According to the illustration’s description, the Kōmori-ba attacks by targeting the eyes of its victims. Although little else is recorded about the creature, it is presented as one of the many strange yōkai that inhabit the supernatural world of Japanese folklore.

Sources

TYZ. (n.d.). 蝙蝠場 (Kōmori-ba). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1065732607.html

Kagewani

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Tradition / Region: Japanese Mythology
Alternative names: Shadow Crocodile
Category: Crocodile

The Myth

Kagewani is a yōkai from the folklore of Yunotsu in Shimane Prefecture. Although its name means “Shadow Crocodile,” it is actually described as a supernatural shark.

According to legend, the creature swims beneath ships and watches the shadows of sailors reflected on the surface of the sea. If the Kagewani swallows a sailor’s shadow, that person is doomed to die.

One tale tells of a sailor who succeeded in shooting and killing a Kagewani while at sea. However, after returning home, he was walking along the beach when a fish bone pierced the sole of his foot. The wound proved fatal.

Later, the bone was identified as having belonged to the slain Kagewani, and the sailor’s death was regarded as the creature’s final act of vengeance.

Sources

TYZ. (n.d.). 影鰐 (Kagewani). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1010654388.html

Hoaya

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Tradition / Region: Japanese Mythology
Alternative names: Boaya
Category: Crocodile

The Myth

Hoaya is a fearsome river monster described in the Edo-period works Nankai Kibun and Hyōryū Tenjiku Monogatari, which recount the travels of the sailor Sontaro after he drifted to foreign lands. The creature was said to inhabit the rivers of Banjarmasin in southern Borneo, where the local people greatly feared it and believed that killing one would inevitably bring misfortune.

The monster was described as resembling a hornless dragon, with a stern face, long manes and ears, four arms, four legs ending in four claws each, and a body measuring between six and thirteen fathoms in length. It often clung to passing boats, frightening those aboard. In another account, its body is said to have been pale black with a yellow belly and lips, extremely hard scales, and a pointed tail ending in three ridges.

According to local belief, Hoaya climbed into the mountains each spring to lay thirty-six eggs, each about the size of a temari ball. After the young hatched and entered the rivers, the parent relentlessly pursued and devoured them until only one remained. That final offspring was then raised by the parent. Boats avoided Hoaya with their young, as they were believed to become especially aggressive.

One night, a Hoaya broke through the decaying fence surrounding a riverside bathing area and attacked a night watchman, biting off one of his legs. The creature became trapped inside the enclosure, where dozens of people eventually killed it after gunfire failed to penetrate its thick scales. The wounded watchman died the following day. Although the Hoaya’s body was thrown back into the river, no further misfortunes followed, despite the widespread belief that killing one of the creatures would bring disaster.

In Nankai Kibun, the creature is identified as Boaya, which is explained to be a crocodile, although its appearance and behavior are described in a far more legendary manner. The account also suggests that the hornless river dragons described in stories from Siam may have been the same creature.

Sources

Landtman, G. (1970). The Kiwai Papuans of British New Guinea; a nature-born instance of Rousseau’s ideal community. New York: Johnson Reprint Corp., p. 302.

Nouma

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Tradition / Region: Japanese Mythology
Alternative names: Wild Horse
Category: Horse

The Myth

Nouma is a one-eyed man-eating yōkai from the folklore of Hinui Village in Ōchi District, Shimane Prefecture.

The creature is associated with the time when iron was produced in local tatara furnaces. One night, while a worker was sleeping at a smelting site, a mysterious woman suddenly appeared and lay over his body.

At the same time, the eerie neighing of the Nouma echoed in the distance. The creature gradually approached the furnace and peered inside through a high window. However, the moment it saw the woman, it immediately fled in terror.

The mysterious woman was later believed to have been Kanayago, the goddess of ironworking and metallurgy, whose presence protected the worker from the man-eating Nouma.

Sources

TYZ. (n.d.). 野馬 (Nouma). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1010655022.html

Umashika

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Tradition / Region: Japanese Mythology
Alternative names: Foolish
Category: Horse

The Myth

Umashika is a yōkai depicted in Edo-period monster picture scrolls, including the Hyakki Yagyō Emaki preserved in the Matsui Bunko collection.

The creature has a beast-like appearance with a long face resembling that of a horse, deer-like hooves, and a single horn. It wears clothing and is distinguished by one eye that protrudes from its socket.

It is believed that Umashika was created through a visual play on the Japanese word baka (“fool”), giving the yōkai its unusual form rather than deriving it from an older folk tradition.

Sources

TYZ. (n.d.). 馬鹿 (Umashika). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1010655018.html.

Umadono

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Tradition / Region: Japanese Mythology
Alternative names: Horse Lord
Category: Horse

The Myth

Umadono is a horse yōkai depicted in the 1788 illustrated work Yōkai Chakutōchō (A Record of the Arrival of Monsters) by Kitao Masami.

In the illustration, Umadono appears among a gathering of yōkai celebrating a feast on an inauspicious day. He is shown beating a drum while a cat dressed in similar clothing plays the shamisen and a fox performs the Shinoda-zuma dance. The accompanying text simply states, “Umadono is beating the drum.”

The image is based on a traditional Japanese metaphor in which “a horse beating a drum” refers to a stallion in heat. Similar depictions of horse monsters playing drums also appear in other kibyōshi (illustrated yellow-covered books) of the Edo period.

Sources

TYZ. (n.d.). 馬殿 (Umadono). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1010654092.html

Uma-ashi

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Tradition / Region: Japanese Mythology
Alternative names: Horse Leg
Category: Horse

The Myth

Uma-ashi is a strange supernatural phenomenon from the folklore of Fukuoka Prefecture in Japan. Rather than appearing as an entire horse, only an enormous horse’s leg manifests.

According to one legend, a horse’s leg hangs down at night from the branch of a tree growing out of an old wall. Anyone unfortunate enough to walk beneath it is kicked by the phantom limb.

Another tradition from Harukoga in Kurume City tells of a gigantic horse’s leg, about ten feet long, descending from a large hackberry tree at midnight. Local people attributed this eerie apparition to the magical powers of a tanuki (raccoon dog).

Sources

TYZ. (n.d.). 馬足 (Uma-ashi). In 新版TYZ 妖怪図鑑. Retrieved June 29, 2026, from https://tyz-yokai.blog.jp/archives/1010655024.html