This may not be what you are looking for, but when I was living in Sapporo I found some really great Japanese artists -- they are closer to experimental and perhaps indie music. They are not the shojo pop type bands at all, but they are excellent Japanese bands. Tujiko Noriko is superb and a great female vocalist. I especially like her albums "J" and "28" They are both collaborations, so J's band is called Ratn, and 28 is with Aoki Takamasa. Both are very moody and intense, but with great beats and well done.
The other recommendation I would have is for Fleckfumie. They sing mostly in Japanese, but sometimes in English or German. Again, they are more experimental, with a lot of electronica etc.
Another band that is like a Japanese stereolab is "Gutevolk" female vocals -- upbeat electronica. In English and Japanese. Good stuff though. The album I have is "Suomi". Oddly, that is also the word for Finland in Finnish...
Finally, if you are feeling extra experimental, you might check out "Tenniscoatsu" The Tennis Coats. The album I have is "boku tachi minna da ne" They are rather weird, but interesting. The girl sings very slowly and in a high pitched voice, the music is very spare, sometimes sing-songy. It's in English and Japanese. It's some weird stuff, but interesting to listen to if only because it is a side of Japanese music that you would never see outside of Japan. I found all of these bands by talking to the hipster proprieter of a tiny hole in the wall record store in Sapporo -- Weird Meddle Records.
