Kitsunetsuki (also written kitsune-tsuki) literally means the state of being possessed by a fox. The fox was believed to enter the body of its victim, typically a young woman, beneath her fingernails or through her breasts. In some cases, the victim's facial expressions were said to change in such a way that they resembled foxes. Japanese tradition holds that the possession can cause illiterate victims to temporarily gain literacy.

Lafcadio Hearn describes the condition in the first volume of his Japanese Fairy Tales:

"Strange is the madness of those into whom demon foxes enter. Sometimes they run naked shouting through the streets. Sometimes they lie down and froth at the mouth, and yelp as a fox yelps. And on some part of the body of the possessed a moving lump appears under the skin, which seems to have a life of its own. Prick it with a needle, and it glides instantly to another place. By no grasp can it be so tightly compressed by a strong hand that it will not slip from under the fingers. Possessed folk are also said to speak and write languages of which they were totally ignorant prior to possession. They eat only what foxes are believed to like--tofu, aburage, azukimeshi, etc.--and they eat a great deal, alleging that not they, but the possessing foxes, are hungry."

He goes on to note that, once freed from the possession, the victim will never again be able to eat tofu, azukimeshi, or other foods favored by foxes.

Victims of kitsunetsuki were often treated cruelly in hopes of forcing the fox to leave. It was not unusual for them to be beaten or badly burned. On some occasions, entire families were ostracized by their communities after a member of the family was believed to be possessed.
 

In Japan, kitsunetsuki was a common diagnosis for insanity as recently as the early 20th century. Possession was the explanation for the abnormal behavior displayed by the afflicted individuals.

Kitsunetsuki is also an ethnic psychosis unique to Japanese culture, which causes its victims to believe they are being possessed by a fox. Some of the symptoms of kitsunetsuki are cravings for rice or sweet red beans, listlessness, restlessness, and an aversion to eye contact. It can be considered a form of clinical lycanthropy.

Possessions by foxes include violent seizures in which the afflicted speak "in the voice of the fox", deriding humans and making demands of priests and practitioners through the body of the possessed.

One ongoing story within the religion tells of a girl in Tokyo who was possessed by two hundred and fifty foxes at once... After being possessed by the fox and making demands of the priest for sake and food, the girl's priest ritually banished the fox, converting it to a kind of universal doctrine and sending it back to the shrine of Inari... It then possessed the girl again and attacked the priest, who "killed" it using okiyome, the practice of a kind of purifying ray from the hands. For months after, the girl would attack the priest suddenly, crying "Attack! Attack!" Reportedly these attempts were being made by the two hundred forty-nine in an attempt to avenge their master.