Cultures all over the world have superstitions about cats, creatures we took into our homes like dogs but never quite tamed, and whose wild, predaceous instincts, although they benefit us when they exterminate pests, are all too unnervingly and visibly well-developed. So it is not surprising that the cat in Japanese folklore is, like the fox and raccoon dog, prone to monstrous transformations.
Long ago many ideas existed about when a cat might become a bake-neko; sometimes it changed when it had been fed in a place for thirteen years and sometimes after only three; sometimes it would be after the cat had reached one kan (about eight pounds) in weight.
Indeed bake-neko could exceed normal cats in size by orders of magnitude, reaching their enormous arms in through doors looking for human prey like an average feline pawing around in a mousehole. They could also take a humanoid form, sometimes devouring people and stealing their identities. A famous bake-neko story involves a man named Takasu Genbei, whose pet cat of many years went missing just as his mother's personality changed completely. The woman shunned company and took her meals alone in her room, and when the curious family peered in on her, they saw not a human being but a feline monster in the old lady's clothes, chewing on animal carcasses. Takasu, with much reluctance, slew what looked like his mother, and after a day had passed the body turned back into the same pet cat that had gone missing. After that Takasu miserably tore up the tatami mats and the floorboards in his mother's room, only to find the old woman's bones hidden there, gnawed clean of flesh.
Cats were also strongly associated with the dead, and a cat belonging to a recently deceased person was viewed with much suspicion, sometimes locked away to keep it from becoming a kasha, a kind of demon that descended from the sky to steal corpses, and which often had a cat-like form. A kind of bake-neko with a forked tail, called a neko-mata, was said to be capable of manipulating corpses like puppets.
As old-fashioned lamp oil was often made from fish, cats could be as fond of stealing the stuff as any yokai, perhaps further cementing their association with the spirit world.
And while cats had a reputation for being ungrateful, they still could have their faithful and even self-sacrificing side, especially when fed by poor owners. Numerous stories of good-hearted cats with magic powers or human-like intelligence exist to explain the symbol of the maneki-neko, the famous ceramic beckoning feline which as a good-luck charm for storekeepers has spread all over the world. There is the cat at a poor temple who beckoned a rich man away from a tree about to be struck by lightning, causing him to become the temple's benefactor; the cat owned by a high-ranking geisha who clawed at her robes to keep her away from the toilet, and even when killed for its strange behavior, still managed to use its ghostly head to bite to death the lurking snake that threatened her; and the cat who appeared in a dream to its poverty-stricken mistress, telling her to manufacture its image in clay in order to bring her wealth. There are also stories about cats taking the forms of women and girls to become wives like foxes, or daughters to childless couples, once again trying to help their human companions make ends meet.
In some places when an old cat becomes a bake-neko, its tail is said to split in two, then it is called a neko-mata or "forked cat". Like most bake-neko, neko-mata are unusually large cats, reportedly a meter and a half long minus the bifurcated tail, and often walk about comfortably on their hind feet. They are said to dance and manipulate the dead like puppets, and are associated with strange fires and other unexplainable occurances. Sometimes the tails of kittens were cut off as a precaution, as it was thought that if its tail couldn't fork, a cat could not become a bakemono.
The group battles a coven of nun's who are actually bake neko beginning in Chapter 393. Kirara is, of course, a neko mata.