An Inugami is a Japanese mythical dog spirit, much like a western familiar—the inugami are loyal to their owners (or inugami-mochi) and serve them and protect them from enemies, but the legend makes it very clear that they are wild, and act on their own instincts, which does occasionally turn them against their owners, and even can bring them to possess them.
Inugami have a very interesting origin legend. But it is said that inugami were created by burying a dog up to its neck, and placing food around it, just out of its reach. As the dog suffers and yearns for the food, the owner would tell them that their suffering is nothing, and eventually as the dog would die, it would turn into an inugami. Because it has died so strongly wanting the food just out of its reach, the food placed before it then becomes a placetory offering for the now-free spirit of the dog, and that service binds the inugami to its owner.
There is another story, though, of a woman who wanted revenge against someone, and so she buried her prized dog in the ground and swore to worship it if it would do her will, then cut the dog’s head off with a bamboo saw. In this legend, the inugami did as she wished, but then returned and haunted her for the cruel way in which she killed him.
As should be obvious, please don’t try any of this at home—it would definitely be considered criminal animal cruelty.
It is believed that an inugami-mochi, or owner of an inugami, will be blessed with good fortune and good health, but in some regions of Japan, it is also believed that the blessing has a curse to it as well—that the inugami-mochi will be shunned by society and unlucky in love. Also, if the owner upsets its inugami, the inugami is likely to turn on the master. If an inugami attempts to return to its body, and the body is no longer available due to decay, the inugami is also likely to inhabit its owner’s body. This is said to bring good health and cure all diseases, but at the same time it is a kind of possession, so not only is the inugami-mochi not in control of his own body, but is also likely to act like, well, a dog. Not the most appealing kind of life.