I'm not up to speed on current japanese music but there were a lot of japanese alt-pop acts around in the '90s: cornelius (especially his 'fantasma' album), pizzicato 5, cibo matto, shonen knife...

if you're happy with some avant-rock or avant-psych-folk stuff, try:

the boredoms
ghost
afrirampo
august born
acid mothers temple

will check for sure, thanks alot

PQ

Pizzicato 5 are great, very twee (like a lot of Japanese stuff), but fun. Not up to date on Japanese music, but a couple of the bands I've come across over the years/

Mikabomb - on the Damaged Goods label, home to the likes of Holly Golightly, the Headcoatees etc. If you like that kind of DIY punk garage thing, definitely worth checking out. http://www.mikabomb.com/

Ex-Girl - Very strange, fantastic live. Saw them in the Lobby in cork a few years ago. Do the best and weirdest cover of James Browns "Sex Machine" ever. http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=56941101

Guitar Wolf - as barkingly mad as the name sounds. Almost a parody of rock and roll but definitely fun. Domo-Kun (google it) likes them

Hanayo does a great electro cover of "Joe Le Taxi", not heard anything else from her to be honest though.
http://www.hanayo.com/
http://profile.myspace.com/index.cfm?fuseaction=user.viewprofile&friendid=72686684

Not Japanese but fronted by a Japanese lead singer - Asobi Seksu, very MBV - http://www.asobiseksu.com/

Hi there,

We put on an amazing Japanese Post rock band called Lite last September. They have stuff on the English record label Transduction (www.transductionrecords.com).

Also we are putting Japanese punk/garage band Electric Eel Shock Saturday March 10th in the Lower Deck

Guitar Wolf. Furious rock'n'roll delivered in Pidgin English. Brilliant.

EDIT/ just saw someone else recommend them, so there you go. 2 votes for the GW.