The oni of Japanese folklore and the demons of Demon Slayer

The Japanese title of the series begins with a single character, 鬼, read oni, which refers to demons. For a Japanese reader, this word immediately evokes a whole imaginary world: the ogres of children’s tales, the monsters chased away every year at the Setsubun festival, the horned creatures of medieval painted scrolls. The series builds on this shared heritage, while inventing its own rules.

Here is what the oni of Japanese folklore are, what Demon Slayer borrows from them, what it changes, and the legends hidden behind certain details of the series. Our page on the Demon Slayer demons presents Muzan and all the Moons, and our article on the meaning of the title Kimetsu no Yaiba explains the character 鬼 that opens the title.

What is an oni?

In Japanese folklore, an oni is an evil creature, often giant, with red or blue skin, horns on its forehead, fangs, claws and terrifying strength. It traditionally wears a tiger-skin loincloth and carries an iron club bristling with spikes. It lives in the mountains, on distant islands or in ruins, abducts humans at night and devours them. It is often translated as “ogre” or “demon”. Some tales make them stupid brutes easily fooled, others cunning lords ruling whole gangs, others still sad beings condemned to wander. This variety left the author great freedom to imagine her own demons, from the most bestial to the most refined.

Oni are everywhere in Japanese culture. They appear in tales, in plays, in prints and in popular festivals. Their image became fixed over the centuries, and many details come from an old belief about directions: the north-east, the ill-fated direction demons were said to come from, was once called the direction of the ox and the tiger, hence the ox horns and tiger skin attributed to them.

The word oni may come from an ancient term meaning what is hidden, invisible. Oni were first formless spirits, responsible for illnesses and misfortunes, before becoming the horned monsters we know. Our article on the Japanese vocabulary of Demon Slayer explains the series’ other Japanese words.

What the series keeps from the oni

The demons of Demon Slayer have kept the essence of their folklore ancestors, starting with hunger. They eat humans, and their strength grows with the number of victims devoured. Many have oni-like physical traits: curved horns on the forehead, protruding fangs, claws, bulging veins, sometimes gigantic size. The father demon of Rui’s family on Mount Natagumo, or the Hand Demon of the Final Selection, look like the monsters of old painted scrolls.

The most powerful demons, on the other hand, often look almost human. Muzan looks like an elegant man, Doma like a handsome smiling young man, Akaza like a fighter covered in tattoos. It is a strong choice by the author: the more dangerous a demon is, the more it looks like us. Monstrosity lies in what it does, not in its face. Muzan takes this idea to its limit: he lives in town, married, the adoptive father of a little girl, and no one around him suspects what he is. Our article on the Hand Demon of the Final Selection presents one of the demons closest to traditional oni.

Hantengu, Upper Moon Four, has horns like a stage oni, and his clones each embody an emotion, anger, joy, sorrow, pleasure, like the masks of Japanese theatre. Nezuko herself grows a horn on her forehead in her awakened form, in the Swordsmith Village. Our article on Hantengu, Upper Moon Four tells about this demon.

What the series invents

The oni of folklore are not particularly afraid of the sun, and they are not killed by cutting their neck with a special blade. These rules are inventions of the series, and they bring its demons closer to the vampires of European tradition: they are immortal, feed on humans, only come out at night, die in the sun and dread a plant, as vampires dread garlic.

The series also invents the system that organises its demons: a single creator, Muzan, who transforms humans by giving them his blood, a hierarchy of Moons, powers specific to each demon, the Blood Demon Arts. None of this comes from folklore. It is this blend of Japanese legends and new rules that gives the series’ demons their identity. A reader who knows the tales recognises the oni, and yet discovers creatures they have never seen elsewhere. Our article on the ways to kill a demon details these rules, and the one on how you become a demon explains the role of Muzan’s blood.

Setsubun, beans and wisteria

Every year, around 3 February, the Japanese celebrate Setsubun, the eve of spring. In homes and temples, roasted soybeans are thrown while shouting “demons out, good fortune in”. A family member often wears an oni mask and pretends to flee under the beans. It is a joyful festival, very popular with children, which drives away misfortune for the year. On that day people also eat as many beans as their age, plus one, for good luck.

Demon Slayer does not use beans, but it takes up the idea of a plant that repels demons: wisteria. Its purple flowers poison them, and the Demon Slayer Corps uses it everywhere, from Mount Fujikasane, where demons are kept prisoner behind a curtain of blooming wisteria, to the houses of allied families, who bear the wisteria crest on their door. Shinobu draws a poison from it, and Tanjiro sleeps without fear in these houses. Our article on the wisteria houses tells about these refuges.

Rashomon, Momotaro and the ogre slayers

Japanese legends are full of oni-slaying heroes, and the series nods to several of them. The most famous is Momotaro, the boy born from a peach, who sets off with a dog, a monkey and a pheasant to defeat the ogres of Demon Island. An ordinary boy, accompanied by unlikely companions, who sets off to destroy demons: the pattern is very similar to that of Tanjiro, Zenitsu and Inosuke. Our page devoted to Tanjiro Kamado, the hero of Demon Slayer tells his journey as a demon slayer.

Another legend tells of the Rashomon gate in Kyoto, where an oni is said to have attacked passers-by before a warrior cut off its arm. In Demon Slayer, Daki and Gyutaro were born in a part of Yoshiwara called the Rashomon riverbank, the most wretched corner of the pleasure district. The name is no accident: it is there that two of the cruellest demons in the series are born. Our article on Daki and Gyutaro, Upper Moon Six tells their story.

The legend closest to the story is that of Shuten-doji, the chief of the oni of Mount Oe, defeated in the Heian era by the warrior Minamoto no Raiko and his companions, who had put him to sleep with poisoned sake. A demon king of the Heian era, warriors who join forces to bring him down, a poison to weaken him: one can see in it an echo of the last battle against Muzan, poisoned by Tamayo and Shinobu before being defeated in the morning.

Masks that protect against evil

Japanese folklore attributes protective power to masks. Masks are hung up to keep misfortune away, worn during festivals and sacred dances. In Demon Slayer, Sakonji Urokodaki carves a fox mask for each of his pupils, which he calls a mask that wards off misfortune. Tanjiro, Sabito and Makomo have all worn one. The Hand Demon recognises them and hunts them down, which gives the mask a tragic meaning.

Our Sabito cosplay takes up his ivory haori and his kimono with a geometric pattern, and our Tanjiro pop figure shows him with his fox mask pushed up on his head, in the collection devoted to Sabito and the pop figure collection. Our article on Sabito and Makomo tells the story of these masks.

Sacred dances and fire

The Dance of the Fire God, Hinokami Kagura, which the Kamado family dances every New Year, also draws on Japanese traditions. Kagura is a Shinto ritual dance, performed for the deities in shrines and villages. Some of its regional forms tell precisely of fights against demons and dragons, with costumed and masked dancers. Tanjuro, Tanjiro’s father, wears for the dance a costume reminiscent of these kagura dancers.

Fire and the sun also play in the series the role they play in many beliefs: that of the light that drives away the creatures of the night. The Dance of the Fire God is in reality Sun Breathing, the only one Muzan truly fears. Our article on the Dance of the Fire God details its moves, and our Tanjiro pop figure with the fox mask is in the Tanjiro Kamado collection.

Oni in Japan today

Oni are not just a memory of old tales. They remain very present in Japanese life. In the Akita region, in the north of the country, men disguised as Namahage, creatures with ogre masks, go from house to house at the end of the year to scare lazy children and bless households. At Setsubun, schools and families replay the demon hunt every February with beans and cardboard masks.

Oni also populate modern popular culture, from manga to video games, often in endearing forms: the ogre has become a character as familiar as the wolf of European tales. The series took advantage of this familiarity. By choosing the word oni, the author spoke to every Japanese reader, then gave her demons a lost humanity that makes them tragic. Our page on the Demon Slayer universe presents the world of the series.

For Halloween or a convention, dressing up as one of the series’ demons is a modern way of playing the oni: terrifying demons always make an impression, and the horns, the eyes marked with a Moon rank or Akaza’s tattoos can be recognised from afar. The Demon Slayer Halloween costume collection gathers the demons and the demon slayers.