Typically, oni have either one or several horns protruding from their scalp. Some have a third eye in the center of their forehead, and they often make a
hideous grimace from ear to ear and showing their conspicuous teeth. Their skin is usually red, black, blue, or yellow and they wear only a loincloth of tiger skin. Although oni are predominantly male, female oni can be as terrifying, as we will see.
In Chinese, the ideogram 鬼 (ki) designate the soul of a deceased person, a ghost, but in Japanese it is read as oni, or demon, but also sometimes as mono, an indwelling spirit or kami. The Encyclopedia of Shinto published by Kokugakuin University in Tokyo, distinguishes 3 type of oni: the wicked spirits or evil kami, the oni as foreigners or strangers, also considered demons, and the oni as good kami. The last type is an oni invoked to chase away evil spirits. The second type of oni typically describes marginalized persons, those from the frontier, foreigners who could have drifted to Japanese shores, or itinerant performers. But the most feared oni are the first type, the ones who bring disasters and death, who were initially considered invisible but later became visible. These malicious beings feed on human flesh; some say they can eat a person in one gulp! Such oni are believed to be the spirits of the deceased who carried resentment during their lifetime, and the spirits of malicious or jealous women are particularly feared …
— Source: “Oni – demons” Dentsdelion Antiques Newsletter Mar-Apr 2012 XII.II
“… Yumemakura fills in the contexts and explanations left out in the original stories so that the readers do not have to read between the lines.
Filling in the gaps, Yumemakura presents the oni’s perspective. This important feature differs from classical literature, in which the oni’s stance is ignored by the authors/compilers or readers. Yumemakura often portrays oni in a sympathetic light, enabling readers to identify with these marginalized creatures. At the same time, Yumemakura peppers the plots of these old stories with a mixture of sex, pathos, and grotesque imagery involving oni and their emotional resonance. As we will presently see, many of his oni are the marginalized spirits of humans trapped in the world of the living by the overpowering urgings of unrequited love.
… a biwa called genjō is stolen by an oni One example of how Yumemakura portrays oni in his own way can be seen in his retelling of “Genjō to iu biwa oni ni toraruru koto” 玄象という琵琶鬼にとらるる こと (A biwa [pipa] called Genjō is stolen by an oni).11
The original story, found under the same title in Konjaku monogatari shū,12 is a straightforward narrative: A prized biwa called Genjō disappears from the Imperial Palace. While the emperor deeply laments its loss, an enchanting melody being played on the biwa is heard from the direction of Rashō Gate. Minamoto no Hiromasa, an excellent musician, follows the tune and discovers an oni at the gate playing the missing biwa. (The reader is never quite sure who this oni is, let alone why the oni steals Genjō and is playing it at Rashō Gate.) Hiromasa asks the oni to return the biwa, an imperial treasure, and the oni obeys. Ever after the biwa acts like a living being—it plays whenever it feels like it.”
The common representation of oni (goblins, demons) in Japanese folklore is of evil, monstrous supernatural creatures malevolent to living beings. However, in recent popular depictions of onmyōji 陰陽師, and by extension Abe no Seimei 安倍晴明 (921?–1005?), in fiction, manga, and film oni are presented as lonely and misunderstood, if still monstrous, creatures. Author Yumemakura Baku 夢枕 獏 (1951–) situates his representations of oni 鬼 in the Heian 平安 period (794–1192). His characterizations of people and oni are, however, informed by a much more modern pathos, evidently very appealing to contemporary Japanese readers and viewers. At a deeper level, the current popularity of onmyōji creatures and characters may well reveal latent Japanese interests in religion and the supernatural that reflect in turn people’s existential anxieties about contemporary life and also their curiosity and interest in some form of afterlife.