Nora neko ] or "stray cats" can be found here there and everywhere. They tend to leave presents for their counterpart humans in the form of poo which come in a variety of shapes/sizes and smells. While folks who have a delicacy for or collect SCP (Stray Cat Poo) would be over the moon to have a free supply of the feline stool, most humans tend not to like having a steaming pile of cack left on their doorstep.
There are a variety of traditional methods called Neko Yoke ] (pronounced "Nehko Yokeh") which are utilized to keep stray cats away - one is in the form of a mat like this with spiky bits on it - the idea is that the spiky bits hurt the cat which would cry like shown in the illustration.
This product is called "Don't Cat" and can apparently be used for stray birds or dogs too - costs 100 yen for a pack of 3.
Don't Cat comes in all shapes and sizes. Not sure how effective it is after seeing the following video though ^^;
When I first visited to Japan, I saw these bottles of water all over the place. They were usually located near a wall or by lamp posts outside houses. I really thought that they were left there for somebody to drink ^^;
On my second visit to Japan, I bothered to ask my friend and he said that they served the purpose of scaring off cats - introducing another form of Neko Yoke. Apparently, reflections in the water are supposed to generate holograms of fifteen feet tall fire breathing dragons which cats dont like.
Another theory (which sounds unlikely) is that the sun's reflections in the water scares cats. This Google Image search will show you how folks use them to attempt to scare off cats, although after seeing this photo, I'm not sure how effective they are ^^;
Are there other methods of cat repellant used in your kingdom?
This is my neighbors line of defense against stray cats ^^;
Any of you are cat owners?