Japan should have its own category simply for the fact that it's still an important market for software.
As an example, the United Kingdom is fairly similar in gaming tastes to the United States. Yeah, UK customers buy some different games in different amounts compared to the U.S. market, but they're generally similar. Japan's taste in games are so vastly different from America and Others, and the rest of the world in general, that they deserve their own weekly chart. Also, you're still proving the point that Japan sells more hardware than the UK.
The main reason Japan has its own weekly chart is not just its software diversity (games that sell well in Japan often don't sell amazingly in the rest of the world), but its sheer ability to sell software. This generation, Pokemon Diamond and Pearl sold about 6 million copies in Japan. And unless my memory's fuzzy, no game has ever sold close to 6 million in the UK, this generation or not. And the USA isn't considered a separate market because it's easier to lump it in with the rest of the Americas. Why keeps those regions separate when their sales are so low? Breaking down the charts into more regions and more countries will just make work harder for the numbers team, and is frankly very unnecessary.
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