If you have never been to Japan and try street photography, it is tough ... Japanese people in general don't like it much when their photo is taken by a stranger, especially a foreign stranger. In Tokyo , where lots of foreigner live, it is not that difficult if you choose the "correct" places.
Having some Japanese friends with similar interests makes it easier. Have a look at gramme_friday's photos at flickr. He lives in Sapporo (like me) and his photos are very good regarding "street photography".
Cheers,
maddoc