These are all examples of outright fake Japanese plates. Many come from car tuning shops in America and there are several different batches. They are sometimes sold as real Japanese car plates by plate dealers (23-96 was recently up for sale by lindken in Germany). Some have also appeared on the Polish language equivalent of Ebay. These all appear to have originated from Ebay car tuning parts dealer speedmotoring in the USA who rightly sells them as plates for show cars.
Genuine Japanese plates are green on white, they have pre-made holes in them and the borders are never painted.
These fakes may be black on white, have no holes or have slots and many have painted borders. Some are made using German dies instead of Japanese ones and many have letters as well as numbers so that they can be put on some of the tuned up Japanese cars for show purposes.
If you are buying on Ebay, check with the photo archives or a plate society or a plate forum or ask somebody about such mint plates.