Female solo
Tomomi Kahala
YU-A
BENI
Akina Nakamori
Seiko Matsuda
Group
B'z (Awesome music.. I'd start with either MONSTER or GREEN. Both are superb albums! <3)
BRIGHT
globe
2NE1
Male solo
Koshi Inaba (Usually, I would recommend listening to Shian first. But, I'm recommending Hadou to start off with instead. It's an album that has a YUI vibe to it. Especially the song "The Morning Call"!
)