Finding Heavy Metal music in Japan?

Hi there, I'm a long-time Heavy Metal fan/collector. I have plan to visit Japan b'cos this is the place where I think I can find the best & precious Metal albums from the world. Just to name a few Metal bands: HEAVY LOAD(Swe), ATTACK(Ger), LEATHERWOLF(USA), etc.
I would appreciate if anyone could recommend me some Metal CD/record stores in Japan that carry quality Metal music CD/LP (new or 2nd hand) at reasonable prices. I intend to purchase the CD/LP for my private collection and also for some friends. I also have intention of starting a small music business in my country therefore any information about finding wholesale supplier of Heavy Metal music in Japan is welcome too.
Many thanks in advance.

I don't really know the type of metal you like, but I really like the bands Concerto Moon, Anthem, Galneryus and Loudness. I also like Hellion Sounds, but that's actually a doujin band: they make metal covers of the games of Square Enix. I really really love them though, because I like synth and fast drumming. :)

Oh yes, I know about Loudness and Concerto Moon and a bunch of Japanese Metal bands like Earthshaker, SLY, Sabbat, etc. By the way, check out this band Blaze from Osaka, pretty cool stuff:
http://www.myspace.com/blazeosaka