I highly recommend flumpool! They have so many amazing songs, and their live shows are made of pure awesomeness! The songs I recommend are: labo, Hoshi ni Negai Wo, Hana ni Nare, Calling, and...bascially everything else. Genre: rock

You may also like Monkey Majik. They mix Japanese and English together. Listen to "Aitakute" it's such a pretty ballad. I also recommend I Miss You and Open Happiness. Genre: pop/rock

Greeeen is pretty good too. I love their song "Be Free."

Asian Kung-fu Generation is good, too. Their song for the movie Solanin, which also is the title for the song, is at the top of my current Itunes playlist. Rewrite is another good song of theirs.

If you like Exile, you may like UVERworld. Sora, Kimi no Suki na Uta, and endscape are some of my favorites of their songs.

Shouta Shimizu has an amazing voice. His songs are mostly R&B/pop. Of his songs, I like Forever Love, Home, and One Last Kiss.

One last artist pimp is for Weaver. They incorporate a piano into thier songs, which is pretty unique for a rock band. Their song "Hard to Say I Love You," was the theme song for the J-drama Sunao ni Narenakute.

Hopefully this helps! : )