Learning fun things about Kitsune possession:
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.
Foxes, though, play a more malevolent role in Japanese folklore. Capable of possessing the souls of the unwary, they have been known to turn their victims into zombies or drive them permanently insane. "You should ask Mrs. Miura about it," Sensei told me. "She lives down at the foot of the hill."
A widow born during the reign of Hirohito's father, Emperor Meiji-she had a portrait of him hanging in her home-Mrs. Miura was a library of information on the subject of kitsune-gami or "fox-spirit possession." She told me about its symptoms. "No appetite, insomnia; hands are cold all the time." Local stories of possession. "You know that road over behind the natural gas store? That's White Fox Lane. Back in the old days a woman who lived over there, every night she'd wake up and fill a bowl of rice and run down to where that bridge is now and leave it. One night the neighbours watched and they saw she was following a white fox. It had possessed her, they said, and was making her feed it." And Mrs. Miura rattled off two family names from the area that had, long ago, been known as kitsune-mochi. These were families, social outcasts that were believed to have kept foxes in their homes, sending them out to perform dark deeds. "Long ago" was a key phrase here, right? I suggested. "Well," Mrs. Miura looked at me. In the mid-1950s, she said, there had been a tragedy when a girl from a hereditary clan of fox-keepers wanted to marry into a "normal" family. The parents of her fiancée forbid it. The lovers both committed suicide.http://www.koryu.com/library/dlowry12.html
Victims of kitsune bewitchment often find themselves tired, exhausted, or ill for days or weeks after their rescue. It’s commonly held that someone who has relations with a kitsune will often be exhausted to the point of death—if they don’t die with the kitsune, they’ll die after being rescued or released. At least one folktale refers to kitsune “sucking the energy” out of victims that way. Hence the suggestion kitsune are vampiric—true in a certain sense. The fox-wife stories lack this aspect..http://www.ranea.org/watts/writing/kitsune.html
Dogs and Kitsune don't get along, btw (which makes it interesting, the conflict between Shippou and InuYasha, and they are very good at looking for weaknesses, and irritating them badly. And he does other things that let you know that Shippou really is based on Kitsune lore.
And for those who wonder about the fertility of hanyous...plenty of stories of families descended from Kitsunes...particularly results in great strength in the descendants. FWIW