I was considering posting samples of music, but then I figured you don't seem really active in this thread, and might miss the expiration date for yousendit files, so I'll just post a description of some bands.
Oblivion Dust was fronted by half-British/half-Japanese Ken Lloyd, and while the band existed he clearly gravitated towards sounds with a more Western feel to them (It's interesting to hear Japanese being sung with an English accent, instead of the other way around which usually ends up with atrocious results). If you get a chance, check out their "Looking for Elvis" album, since I felt that that release was most reminiscent of '90's-era Seattle-based rock groups. "Butterfly Head" is a longstanding favorite among fans, myself included, and it showcases their distinctive darker side with songs like The Nude and Again. I'd stay clear from the "Reborn" album, as it imitates Western post-grunge bands too closely without adding anything new.
Luna Sea was a popular rock group that was split into different stages. Their first indies release, Luna Sea, was dark, gritty, and had a very rough feel. Although it lacked the refined production of later eras, their songs from that period are still fun and enjoyable to listen to.
Their next two albums, Image and Eden, showed that the band knew how to evolve, and evolve well. Image continued with the dark feel of the band, with production sounding a little better, although the relative loudness factor of the previous era was waning in favor for better articulation in sounds. The Eden album, as the name implies, had a more mystical feel to it, and did away with the relative darkness of the last two albums. Soothing sounds such as Recall and Providence coupled with the absolute beauty of Lastly, with its richly delayed guitar distortions, mark this album as one of my favorites.
The next two albums, which I believe would be Mother and Style, continued their success, with the former of those two being the most popular album of theirs. I felt Style was a bit bland, but Mother returned them to the darker parts of their earlier days but with a much better quality in production and songwriting.
They split up some time after (forget when exactly) but when they returned with Shine and Lunacy, their style was much, much more clearly refined, utilizing better and clearer guitar and bg sounds that didn't sound as rough. It was, ironically, at this time that fans criticized them as being too "mainstream" and "poppy." However, this era did not find them compromising their musicianship, but actually expanding it. They split up after Lunacy.
Definitely check out X Japan. I don't listen to them that much, but you'll probably like them. They're essentially a metal band with a good melody. Sometimes they mix in ballads into their music, but this doesn't tend to sound corny (except on the Dahlia album).
Daita released one album as far as I know. It was founded by the guitarist of Siam Shade (another rock band). The album itself is basically guitar instrumentals a la Joe Satriani, but with a mostly soundtrackish backing. Unfortunately, some of the songs sound amateurish with corny melodies, but if you're into guitar instrumentals, this might be worth a look.
Maybe check out Hide, a widely known rock musician (not Hyde, although I prefer Hyde better) who committed suicide. I actually have a couple of Hide's albums on my computer but can never really get into them. Still, he's a favorite among many.
There's more, of course, but this should get you started.