Japan is not a western country. Western countries are those with common historical and cultural roots springing from Roman civilization. Christianity, the Roman alphabet, our languages, our scientific and philosophical traditions all spring from that one source. With Japan and many other Asian countries, the root of their culture, religion, science, philosophy and language is in China. They are completely seperate.

If you are talking about Japan's modern economic and political make up, it would be more accurate to call it a northern country rather than a western country.