Suggestions on Female Japanese artists?

[BlackSilence]

UM I'm in desperate need for new music since my favorite from males' doesn't do anything musical these months, and I'm kinda in need for something else than Ayu...But I have no idea what I should check to not waste time looking for something...so...Could someone suggest some japanese female artsists who would have strong voices like Koda's or Ayu's and some good powerful songs with a little of rock flavour in up-beat and rich sounds in ballads?

Thanks in advice!