Tradition: Japanese Mythology
Alternative Names: 白鼠の番頭, White Rat Head Clerk
Category: Rat

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The Myth

Shiro Nezumi no Bantō, or the White Rat Head Clerk, is a folkloric figure based on the traditional belief that white mice are messengers of Daikokuten, a deity associated with wealth and prosperity. A white mouse living in a household was considered an auspicious sign that fortune would come to its inhabitants. The term shiro nezumi consequently became a metaphor for a loyal and capable head clerk or employee whose service helped a merchant’s business prosper. By contrast, dishonest servants who stole from or harmed their masters were called kuro nezumi, or black rats.

In Kotowaza Heso no Yadogae, the White Rat Head Clerk is depicted literally as a white rat, working with an abacus while admonishing the retired head of a merchant family. He asks where the young master has been since the previous day, noting that rumours about his behaviour are spreading and criticising the elder for being too lenient with his son.

The retired merchant, portrayed with extraordinarily long eyes that extend beyond his face, brushes aside the clerk’s concerns and reassures him that his vigilance is appreciated. Nevertheless, he appears unwilling to discipline his son’s extravagant lifestyle. The scene uses humour and visual exaggeration to contrast the diligent, responsible employee with a wealthy patriarch who continues to indulge his wayward heir.

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Sources

“Shironezumi.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1077096672.html

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Tradition: Japanese Mythology
Alternative Names: 鼠の化物, Rat Monster, Mouse Monster
Category: Rat

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The Myth

Nezumi no Bakemono is a satirical yokai described in Ōmachi Keigetsu’s Eiri Kunwa, published in 1916, in a section titled Hyakki Hirugyō. It is listed as the thirty-eighth of forty-one monsters and depicts a rat standing upright on two legs in a comical pose.

According to the account, an outbreak of plague led authorities to purchase rats for five sen each. Alarmed by this development, the rats transformed into monsters. Yet even after changing their forms, they retained their natural habits of gnawing and stealing. Their sharpness of tooth varied: those with poor teeth gnawed at their parents’ shins, while those with somewhat sharper teeth gnawed at their masters’ households.

The satire extends beyond ordinary theft. Some of these creatures gnaw away at government salaries and positions, the wealth and livelihoods of the people, and even learning, religion, and morality. However, they consume these things without understanding their true value. The author laments that the world has become overwhelmed by such monsters, using the rat’s habit of gnawing as a metaphor for people who exploit others, misuse their positions, or take only fragments of knowledge for personal gain.

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Sources

“Nezumi-bakemono.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1077096665.html

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Tradition: Japanese Mythology
Alternative Names: 小玉鼠, Kodama Mouse, Kodama Rat
Category: Rat

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The Myth

Kodama Nezumi is a supernatural creature known among the matagi, traditional hunters of Akita Prefecture, particularly in Kitaakita and Senboku districts. It resembles a swollen Japanese dormouse and is said to suddenly burst with a loud popping or explosive sound. Hearing this noise was considered an ominous sign that foretold failed hunts and other misfortunes. In some communities, the sound was believed to signal the displeasure of the mountain deity, and hunters who heard it were expected to return home rather than continue into the mountains.

Regional traditions describe the creature bursting along its back, and hunters recalled its sound as either louder than a gunshot or a soft, sudden pop. Some believed that reciting a protective Buddhist invocation three times could help ward off its influence, although speaking about the creature itself was also considered unlucky. The sound was associated with accidents and disasters, including a tale of a hunter whose sleeping shelter caught fire after he heard it.

Legends about the creature’s origin tell of a woman who sought shelter in a mountain hut during winter. One group of hunters refused her because women were forbidden in the mountains, while another took pity on her and offered her lodging. The woman, revealed to be the mountain deity, gave birth to twelve children on branches of the mizuki tree before flying away. The hunters who sheltered her were rewarded with good fortune, while those who rejected her were transformed into Kodama Nezumi. According to some versions, the transformed hunters resented their fate and caused misfortune by bursting with a loud noise.

Despite its supernatural reputation, Kodama Nezumi is identified in folklore research with the Japanese dormouse, a small mammal that hibernates curled into a ball. During winter logging, dormant dormice could tumble out of trees, and workers reportedly called them kinoko-tama. Folklorist Mutō Tetsujō suggested that the creature’s name and its echoing burst might be connected to kodama, the Japanese word for an echo or a tree spirit.

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Sources

“Kodama Nezumi.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1010654298.html

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Tradition: Japanese Mythology
Alternative Names: 旧鼠, Old Rat, Aged Rat
Category: Rat

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The Myth

Kyūso refers to an old rat that has acquired supernatural qualities through age. It appears in Japanese works such as Ehon Hyaku Monogatari and Okina gusa, where it is associated with extraordinary strength, unusual behaviour, and strange relationships with cats and humans.

In Ehon Hyaku Monogatari, one account describes a rat from Shigi in Yamato with red, black, and white fur that habitually caught and ate cats. Another tale, set in Dewa during the late fifteenth century, tells of an old rat that had lived undisturbed in a stable for generations. After the household cat died from poison, the rat reportedly nursed and raised her five kittens before eventually disappearing. This remarkable story was passed down to Matsuo Bashō through Kawai Sora. The same book also references a tale from the Chinese collection Taiping Guangji involving an old rat that entered into a relationship with a human woman.

A different account in Okina gusa, set in Nagoya around the beginning of the Hōreki era (1751–1764), describes a gigantic old rat that repeatedly stole oil from a household lamp. When confronted by cats, it killed one by biting its neck. Eventually, however, another cat defeated the rat by remaining still until the creature attacked, then killing it with a bite. These stories portray the Kyūso as a formidable creature whose extraordinary age grants it unusual abilities, while also exploring the shifting relationship between cats and rats.

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Sources

“Kyuso.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1076714120.html

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Tradition: Japanese Mythology
Alternative Names: 鼠鬼女, Rat Demon Woman
Category: Rat

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The Myth

Nezumi Kijo is a yokai mentioned in the Japanese work Tōsei Kojitsuke Kaiō (当世故事附選怪興). It is said to leave unharmed those who carry a protective talisman used in religious rites, while those without one are threatened with a poisonous breath described as the intimidating menace of a gatekeeper.

The creature’s name is a play on nezumi-kido (鼠木戸), a narrow entrance gate used at theatres and other entertainment venues. These gates were designed to prevent people from entering without paying. Because visitors had to crouch and squeeze through them, they were likened to mice entering a hole.

Nezumi Kijo’s behaviour reflects the gatekeepers who guarded these entrances: paying visitors carrying their admission money were allowed inside, while those attempting to enter without paying were intimidated and turned away. The yokai appears to be a humorous personification of this practice rather than a creature described through an independent body of folklore.

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Sources

“Nezumikijo.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1076912062.html

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Tradition: Japanese Mythology
Alternative Names: 鉄鼠, Iron Rat, Raigō Nezumi
Category: Rat

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The Myth

Tesso, meaning “Iron Rat,” is a monstrous supernatural rat born from the vengeful spirit of the Buddhist monk Raigō. During the reign of Emperor Shirakawa, Raigō served as abbot of Mii-dera in Shiga Prefecture. After praying for the birth of a royal heir, he was promised permission to build a new ordination hall at his monastery. However, the powerful rival temple Enryaku-ji pressured the Emperor into breaking his promise. In despair and anger, Raigō undertook a hunger strike and died after one hundred days.

Consumed by resentment, Raigō became an onryō, a vengeful ghost. His spirit was said to have appeared near the young Prince Taruhito, who died soon afterward, leaving the Emperor without an heir. Raigō’s spirit then transformed into a gigantic rat with a body as hard as stone and teeth and claws as strong as iron.

Tesso summoned a vast army of rats and led them against Enryaku-ji on Mount Hiei. The creatures gnawed through the monastery’s buildings, destroyed its furnishings, and devoured sacred Buddhist texts, scrolls, and even statues of the Buddha. The devastation continued until a shrine was established to appease Raigō’s spirit. According to tradition, Raigō’s shrine faces north toward Mount Hiei and Enryaku-ji, the monastery at the centre of his legendary vengeance.

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Sources

“Tesso.” Yokai.com. https://yokai.com/tesso/

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