Oni, the Demons of Japan

The oni has deep and tangled roots. The word is written with the Chinese character gui, which in China meant a ghost or the spirit of a dead person. In Japan the meaning shifted. In the 930s the scholar Minamoto no Shitagō explained in his dictionary that oni came from on, ‘hidden’, because these beings did not wish to be seen. Many scholars accept that early oni were invisible, dangerous presences rather than the horned giants of later art, though the origin of the word is still debated.

Some of the earliest written stories are already frightening. The Izumo Fudoki of 733, a record of the province of Izumo, tells of a one-eyed oni that appeared while a man was working his fields and devoured him. At court, meanwhile, demons were understood as bringers of epidemic disease. The chronicle Shoku Nihongi records that in 706, during an epidemic, the court performed the tsuina, a ceremony adapted from China in which a masked exorcist drove demons of pestilence out of the palace at the end of the year.

Buddhism added another layer. Japanese Buddhists absorbed Indian and Chinese teaching about hells, where wardens punish the dead, and about demons who obstruct the path to awakening. Painted scrolls of the hells from the 12th century show muscular, horned tormentors, among them the ox-headed and horse-headed guardians known as Gozu and Mezu. By the late Heian and Kamakura periods these images had merged with native ideas, and the oni took the form that became classic.

The standard oni is huge, horned and fanged, with red or blue skin, wild hair, a loincloth of tiger skin and an iron club studded with spikes. A popular explanation links the horns and tiger skin to the kimon, the ‘demon gate’ in the north-east through which evil was believed to enter. In the Chinese zodiac this direction is that of the ox and the tiger, so a creature with an ox’s horns and a tiger’s pelt fits its place. Whether this explanation is the origin of the image or a later rationalisation is uncertain.

In stories oni live on the margins: in mountains, on distant islands, at ruined gates. They steal women and treasure, eat human flesh and spread sickness. They can change shape, appearing as a beautiful woman or a harmless old man. Thunder itself was pictured as an oni: the thunder god Raijin is often painted as a horned figure beating a ring of drums.

Yet oni are not pure evil. Folklorists such as Komatsu Kazuhiko have argued that oni often stood for outsiders: mountain peoples, bandits, those outside the order of the capital. Oni can also be turned to good purpose. Fierce oni faces on roof tiles, onigawara, guard buildings, and in Buddhist art oni appear as converted beings who serve the Buddhist teaching. The line between demon and guardian is thin.

A well-known Buddhist example is Kishimojin, the Japanese form of the Indian Hārītī. In the story she was a demoness who devoured other people’s children until the Buddha hid one of her own hundreds of offspring, teaching her a mother’s grief. Converted, she became a protector of children and of childbirth, and she is still worshipped at temples of the Nichiren tradition, among others. Not every oni, either, is male. Tales of the kijo, female demons, often describe women turned into oni by rage, jealousy or betrayal, such as the woman of Uji who, in one medieval story, prayed to become a demon to take revenge on a faithless lover. In these stories the oni is less an alien monster than a warning about the passions that can transform a human being.

The most famous oni tale is that of Shuten-dōji, the ‘drunken boy’, a demon king who lived on Mount Ōe near Kyoto and carried off young women from the capital. According to the 14th-century scroll Ōeyama Ekotoba and many later versions, the warrior Minamoto no Raikō and his four retainers went to the mountain disguised as mountain ascetics. With divine help and drugged sake, they made the demon drunk and cut off his head. The story was retold in illustrated books, Noh plays and woodblock prints for centuries.

One of Raikō’s retainers, Watanabe no Tsuna, appears in another tale, in which he cuts off the arm of an oni at the Rashōmon or Modoribashi bridge, only for the demon to return in disguise to reclaim it. The folk tale of Momotarō, the Peach Boy, who sails with a dog, a monkey and a pheasant to conquer the oni of Onigashima, Demon Island, spread widely in printed form in the Edo period and became one of Japan’s best-known children’s stories.

Noh theatre gave the demon a tragic face. The Hannya mask, with horns and an anguished grin, represents a woman transformed by jealousy, as in the plays Aoi no Ue and Dōjōji. Here the oni is not a monster from outside but what a human being may become.

The yearly struggle with oni survives in Setsubun, the day before the traditional start of spring, around 3 February. The court expulsion rite gradually became a household custom, and bean-throwing is recorded from the 15th century. Today families scatter roasted soybeans, shouting ‘Oni wa soto, fuku wa uchi’, while temples and shrines hold public ceremonies, often with celebrities throwing beans to crowds. A few places with special ties to oni, such as Kinpusen-ji at Yoshino, change the cry to welcome the oni in.

Oni remain everywhere in Japanese life. Children meet them at Setsubun and in picture books; the phrase oni-gokko, ‘playing oni’, is the Japanese name for the game of tag, and the player who is ‘it’ is the oni. In the Oga peninsula of Akita, men dressed as the Namahage, with fierce masks and straw capes, still visit homes on New Year’s Eve to scold lazy children and bless the household. In 2018 UNESCO recognised the Namahage and similar customs as intangible cultural heritage.

Modern popular culture has made oni both villains and heroes. Lum, the horned alien girl of Takahashi Rumiko’s manga Urusei Yatsura, begun in 1978, borrowed the tiger-skin oni look. The manga and anime Demon Slayer (Kimetsu no Yaiba) made demons called oni the centre of a worldwide success, and oni appear in countless video games. These works often give the oni a backstory and a sorrow, continuing an old Japanese sense that demons may once have been human and may yet be reconciled.