Beerzilla,
Don't know, but Ginga's been at it for a while and I suspect it's a house strain.
You can get hefe yeast in Japan. You can order beer for delivery online, or get it from an online HBS.
Order non-Japanese beers from Ezo beer:
http://www.ezo-beer.com/eng/index.htm
Order Japanese beers (sorry, no English) from:
http://www.craftbeers.jp/
Here's a list of more links:
http://www.bento.com/rev/beeronline.html
Due to JP laws, I don't want to put the HBS URL here, but PM me if you're interested.
You can always have stuff shipped from the US or Australia too. That's what I do when all else fails.