They are not really the same. In fact, they are not both fox spirits with nine tails.
Left: A nine-tailed fox depicted in the ancient Chinese bestiary Classic of Mountains and Seas
(山海經) | Right: A distinctly single tailed kitsune depicted in the Japanese almanac
kin mou zui (訓蒙図彙)
The fox spirits of later Chinese traditions do not necessarily have nine tails, either. Similarly, Japan later imported the Chinese nine-tailed fox, but it found a place in Japanese folklore as a distinct entity separate from the traditional kitsune.
Although they share notable similarities, such as transformation and betwitching humans, the Japanese kitsune and the Chinese hulijing actually have fundamental differences.
In the Japanese language, the word
kitsune literally just means "a fox". There's no difference between that and the fox as an animal. As this would imply, the kitsune are regarded as simply common foxes, though held to be naturally long lived and attributed with magical abilities.
In contrast, the Chinese
hulijing means specifically a "fox spirit". They are no ordinary foxes, but instead the result of centuries or even millenia of training. Some tales further describe them as engaging in powerleveling through essence-sucking intercourse with mortal humans à la western succubi or incubi.
The Classic of Mountains and Seas for instance mentions that:
There is a beast, which is shaped like a fox but has nine tails, and sounds like a baby. It eats men; eating it wards off evil.
Which clearly shows that the fox spirit is considered distinct from normal foxes.
There is also a host of minor differences, such as the kitsune's reputed love for fried tofu versus the hulijing's preference for eggs.
Another major difference exists in the worship of the two entities.
In traditional Japanese folklore, the kitsune have an essential feature as messengers of the god of rice productivity and prosperity, the
inari ōkami (稲荷大神).
In Japan, however, the fox known as kitsune has since the eight century been enshrined and worshipped in a pervasive network of sacred associations in connection with Inari. The widespread cult portrays kitsune as a divine messenger of the rice god who promotes agrarian fertility as well as productivity and prosperity in a much broader sense.
- Heine, Steven. Shifting Shape, Shaping Text: Philosophy and Folklore in the Fox Kōan. University of Hawaii Press, 1999.
The association had formed as early as the 8th century and remains extremely strong to this day. The kitsune continues to feature in tens of thousands of Inari shrines across Japan, as recipients of fried tofu and rubbing by sickly miracle-seekers.
A stone kitsune at the Fushimi Inari Taisha, the chief shrine of the Inari god.
In contrast, in Chinese folklore fox spirits have a much more ambiguous standing. For instance Ji Xiaolan in his Notes of the Thatched Abode of Close Observations that:
Dark and light are different, but foxes are between dark and light. Humans and objects are different, and foxes are between humasn Hsien and Yao are different, but foxes are between the two.
Unlike the worship of kitsune in major shrines as messengers of a rice god, the foxes of China were prayed to in private homes as one of a group of five animal spirits. Exact compositions vary, but these typically includes weasels, snakes, hedgehogs and rats. Families would offer sacrifices in the hopes of receiving protection.
There is no real evidence that the Chinese and Japanese versions share a common origin. Fox worship is ancient in Japan; the earliest documentation of fox folklores appeared in the late 8th century
nihon ryōiki (日本霊異記), lit. Chronicles of Supernatural Tales of Japan.
That is almost as early as the first written works of any kind in Japan, and reelates the tale of a fox assuming the form of a woman and marrying a human. The tale claims the incident to be the origin of the term kitsune, but that is almost certainly an invented etymology.
(very roughly) During the reign of Kinmei Tennō, a man was looking for a bride and met a pretty woman who was looking for a husband. They started sleeping together and produced a baby boy on December 15. Tthe family dog gave birth too and the puppy was aggressive towards the woman, chasing her. Frightened, she turned into a
yakan and fled. The man saw and pled, "You and I have a child together, I cannot forget you. Come (
kitsu) back to sleep (
ne) at least." She agreed. This is where the name
kitsune comes from (...)
The Japanese kitsune ultimately absorbed elements, particularly of malice, from the Chinese hulijing. Both traditions were further affected by the Indian version, which spread through both China and Japan by way of Buddhism. The Buddhist spirit ḍākinī for example was syncretised with native Inari worship to become a fox spirit.
The nine tailed fox, additionally, was introduced to Japan both as a general concept as well as a specific ancient fox spirit from India. It is said to have tried to overthrow an ancient Indian kingdom, and later brought about the Shang Dynasty's downfall as Consort Daji. The spirit eventually made it to Japan and became Tamamo-no-Mae before being exposed and vanquished.
The Nine-Tailed Fox terrorising Indian Prince Hanzoku, by 19th century painter Utagawa Kuniyoshi