Chihiro Onitsuka has such powerful vocals

It is very impressive.
Shiina ringo has awesome vocals...when she wants too...

However most of the time she forcefully make weird annoying proposital noises with her voice which aren't very nice. But when she's singing more seriously (and less crazier) her voice sounds great.
Mika Nakashima's voice sounded so immature at her debut. It has been evolving way too surprsingly so it won't be long before her voice turn into something pretty awesome because it seems to be getting better and better.
I love KEIKO's voice too. Her voice is quite unique and it adds such a great contrast to the "a song is born" single version.
Misia can sing better live than in studios...it is amazing...I just wish her songs were a bit more interesting since I think it's such a waste of a great voice