Every culture has it's own mythology and fantastic tales which are used at least in part to explain weird or unusual occurences that otherwise would be left unexplained and the Japanese culture is no exception.
The Yokai, are supernatural otherworldly creatures that are similar to the fae of European cultures. Having no distinct alignment, these Yokai can be helpful or unhelpful, kindly or callous. Often they appear in animal form, or as humans with animal like features or even both, shapeshifting being commonly attributed to many Yokai.
Amongst these Yokai, belong the Nekomata. These creatures live in the mountains and have been known to attack, kill and eat anyone unlucky enough to encounter them. Chances of an encounter were obviously influenced by how deep you were in the mountains and Nekomata used various tricks such as mimicking the cries of people in danger, to lure their prey further away from the safety of their homes and deeper into unknown territory where they could be eaten. There is some indecision as to how these terrifying creatures actually look, especially as they were also known to be able to change from their animal their form to that of a humans. Normally however, they were said that they have the head of a cat and the body of a very large dog which sounds like something you'd definitely want to avoid, supernatural or not.
Not all Nekomata were like this however, in fact some start off life not in the mountains, but in peoples homes as house cats. It was thought that these domesticated kitties would, as they grew old, develop the power to bewitch and entrance their owners. They would eventually turn into nekomata and vanish off into the mountains, presumably to live with their mountain cousins, killing and eating humans.
For this reason, people came to believe that they should not raise a cat for too long in case this happened, for it was only domesticated cats that turned. Perhaps a cruel fate for a cat that has been domesticated to be turfed out into the cold but it was common lore that it was necessary to avoid the nekomata transformation.
It wasn't just murder that was within the powers of the nekomata, this demon cat was said to enjoy speaking with spirits, controlling the dead and shapeshifting into human form purely to spread mischief and misery amongst the people. One particular trick for example was to taunt people with visions of their dead loved ones. Fortunately, the brunt of their malevolence seems to be directed specifically towards those who had caused them harm during their mortal years, prior to their ascension to magic hell cat status!
Bakeneko, a far less malevolent
Yokai, often associated with Nekomata.
Now this transformation into Nekomata was believed to be accompanied by one particularly obvious physical manifestation, that of the cat possessing two tails, or looked at a different way, a forked tail. So strong was this belief that the tails of cats were sometimes cut off at a young age in order to stop the change. No wonder these cats were believed to wreak revenge on their wrongdoers, in fact the strength of the Bananeko was directly proportional to the amount of abuse and suffering they had endured as a house cat, before changing.
So next time you think about scolding your cat for jumping on the table, or dancing on the keyboard like one of mine is doing right now, maybe you should give it some biscuits, a little attention and just be content it's not practicing necromancy.