I've Sound (Aibu): http://en.wikipedia.org/wiki/I%27ve_Sound
which includes: Kotoko, Mell, Mami Kawada (川田まみ), Eiko Shimamiya (島みやえい子) (and others...)
These singers may not have the beauty of someone like Namie Amuro or Koda Kumi, but their singing ability is excellent. Their music styles include trance, techno, hard rock, and soft rock as well. They also do a lot of anime music in a similar vein as Nami Tamaki.
If you just want straight up rock music, try Kaela Kimura...
Japanese music is extremely diverse, and you'll get as many different opinions as there are people to post them.
If you haven't already, I would suggest getting a free account with www.imeem.com where you can listen to these and other musicians from all over the world.
dj krush, kyoto jazz massive, jazztronik, silent poets, monday michiru, soul bossa trio, tha blue herb, tokyo ska paradise orchestra, cro-magnon, bull jun, AYB Force,loop junktion, mondo grosso,,,
Well I listen to a lot of Japanese R&B and some pop. Some artists that I like are: CHEMISTRY, EXILE, COLOR, Bonnie Pink, Crystal Kay, m-flo, Amuro Namie, Tokyo Jihen, KAT-TUN, SATOMI', DOUBLE, Kubota Toshi, Hirai Ken, SOULHEAD, MISIA, Koda Kumi, and Utada Hikaru.
I agree with what わからひ is saying about listening to Japanese music with English in it. I'm an American listener who listens to a good bit of Japanese music and studies the language but it still strikes me as very strange. I've heard Russian singers t.a.t.u. try to add Japanese words in one of their songs and a translation song of Six Pence None the Richer's Kiss Me, and those were pretty bizarre. Most of the time when I hear songs with "Engrish" in it, I just think it's kind of amusing rather than take it seriously.
From my experience I`ve noticed that alot of Japanese R&B and rap songs have English in it. But it tends to make more sense than it does in some typical J-pop songs. I think what`s interesting is that there are artist that will use katakana English and "normal" English in there songs. Utada Hikaru does this a lot. But maybe that`s because she`s fluent in English though. But English in songs don`t really bug me. A lot of artists do this kind of stuff. Quite a few American artists have used Spanish in there songs. And I`ve heard random French in songs as well. I guess people think using other languages just make the songs sound cooler.
I'm so happy to see another "gaijin" who likes Kuroyume and Kiyoharu.
Kuroyume is one of my all-time favorite bands, they have so many awesome songs.
I have seen Kiyoharu in concert 3 times as well.
I have been desperately searching YouTube for a video I once saw there, it was a concert of Kirito where he performed "Boukyaku no Sora" (SADS) live with Marty Friedman and Kiyoharu...maybe it was removed from YouTube or something, I can't find it anymore, but if anyone knows what I'm talking about or at least if that clip is available on a DVD or something, please let me know!
I like mostly older Japanese rock bands...
X Japan
Luna Sea
even old L'arc and Glay and Janne da Arc but I don't like their recent stuff, it sounds too much like plain pop-rock for me.
The newer band that I've heard and like is Merry. Something about their guitar sound...it's something that other bands lately have been lacking...a nice, warm guitar tone and catchy riffs.
Don't really listen to much pop but I sometimes listen to Koda Kumi and Utada Hikaru. I used to not like Hamasaki Ayumi, but she's got more songs that I do like than I originally realized.
And for a heavier sound, I recommend Sex Machineguns (these guys are soooo funny but their music is also really good) and Onmyouza (sound kinda like Iron Maiden with a female singer).
Lately I listen to lots of electronic music though so I'm not really up-to-date on rock and pop stuff.