This is a photoshop. The only playable demos at the moment are at GamesCom, so they would either be in English or German, not Japanese.
The original source claimed this was from PokemonSmash, despite the fact it doesn't air for another hour and 15 minutes.
there was a japanese demo...
There was, but then the image would have been released last week when the Japanese demo was available, no? Not while the German one is running. If there's a language select, the point is moot either way.
The source of a lot of these images is 4chan, people are colour editing things to troll everyone. http://i.imgur.com/zVs5aep.jpg