Kitsunetsuki (狐憑き or 狐付き; also written kitsune-tsuki) literally means the state of being possessed by a fox. The victim is always a young woman, whom the fox enters beneath her fingernails or through her breasts.
Kitsune (狐, IPA: [kitsɯne]) is the Japanese word for fox. Foxes are a common subject of Japanese folklore.
Ono, an inhabitant of Mino (says an ancient Japanese legend of A.D. 545), spent the seasons longing for his ideal of female beauty. He met her one evening on a vast moor and married her. Simultaneously with the birth of their son, Ono's dog was delivered of a pup which as it grew up became more and more hostile to the lady of the moors. She begged her husband to kill it, but he refused. At last one day the dog attacked her so furiously that she lost courage, resumed vulpine shape, leaped over a fence and fled.
So every evening she stole back and slept in his arms.
Because the fox returns to her husband each night as a woman but leaves each morning as a fox, she is called Kitsune.
In classical Japanese, kitsu-ne means "come and sleep", and ki-tsune means "always comes".