Granted, this is a long shot (given I haven't seen the whole movie) but this is from the ImDB database.
"Chin Chin"
Written by Damien Wagner
Performed by Bang Wu Cherry and DJ Dune
Features "Japanese Schoolgirl Rap"
Played in the Night Club scene
However, there are three other listings for Japanese bands, so here's the link I got it from:
http://us.imdb.com/title/tt0120611/soundtrack