Ungaikyō

The ungaikyō is a yōkai in Japanese folklore or fiction, a type of mirror monster.
The monster is depicted in the Gazu hyakki tsurezure bukuro, a collection of yōkai paintings by the Edo period ukiyo-e artist Toriyama Sekien.
Modern commentary considers it an example of a or possessed object often depicted with faces, etc., and the ability to maneuver.

Mythology

Toriyama Sekien illustrated the "Ungaikyō" in his, published in Tenmei 4/1784. As the title suggests, this work was a collection of haunted objects or tsukumogami.
Sekien drew "Ungaikyō" as a mirror with a mischievous looking face, held up on a tree-like stand. Accompanying the drawing is the commentary as follows:
The, in Chinese literature, is a legendary mirror that is said to reveal the true identity of demons, as Sekien states at the beginning of his commentary.
The shōmakyō in historical fiction was said to have revealed the true identity of Emperor Consort Daji of the crumbling Shang dynasty to have been the nine-tailed fox, according to, e.g. a Japanese adaptation of the Ming period novel Fengshen yanyi.
The ungaikyō in Gazu Hyakki Tsurezure Bukuro is noted to be an original creation of Sekien Toriyama based on the shomakyo, and the accompanying picture shows it to be a mirror with a monstrous and mysterious face floating on it, as can be seen in the figure.

Modern commentary

Books on yōkai since the Heisei era describe the ungaikyō explicitly as a tsukumogami. According to some, the ungaikyōs face reflects the face of the yōkai that possessed it. Another scenario is that whichever yōkai reflected in the shōmakyō will gain control of the mirror and manipulate it.
One linguistic conjecture is that the name “ungaikyō” had been a pun played on Sengaikyō, the Japanese pronunciation of the Chinese geography treatise Shanhai jing, which describes a number of yōkai.
The possessed mirror manifests such characteristics as manipulating people's reflections to resemble what they prefer, transforming any human who looks into the ungaikyō into a monstrous version of themselves as the reflection shown, or to trap spirits in them.

The mirror monster

In a book written by yōkai manga artist Shigeru Mizuki, there is a legend that on the fifteenth night of the eighth month of the lunar calendar, if one fills a quartz tray with water under the moonlight, and use that water to trace an image of a yōkai on the mirror, that yōkai will then dwell inside the mirror.

In popular culture

The ungaikyō in the 1968 film Yokai Monsters: Spook Warfare is designed as a yōkai in the shape of a raccoon dog. In the film, it has the ability to inhale and puff out its belly into a sort of giant TV screen, then display scenes from various places.
It is pointed out that many yōkai illustrated books for children since the Shōwa era often ascribes a raccoon dog-like appearance to the ungaikyō and gives it the ability to show images on its pot belly due to the influence of the aforementioned film.