At 35, Shutoku Mukai is practically the elder statesman of Japanese indie rock. The guitarist and singer, whose nerdy demeanor suggests an off-duty salaryman rather than a rock star, has been behind some of the most abrasive and inventive music to make a dent in Japan's pop charts during the past 10 years, inspiring a generation of off-kilter guitar slingers.

Mukai made his name as the frontman and creative force behind pioneering indie act Number Girl. That band's nervy, clamorous rock — indebted to American guitar heroes such as Pixies and Sonic Youth — enjoyed considerable success at the turn of the decade, paving the way for the likes of Asian Kung-Fu Generation and Rin Toshite Shigure.

When Number Girl broke up at the peak of their fame in 2002, Mukai resisted the temptation to rehash past glories and instead turned his attentions to what had until then been a side project, Zazen Boys. Recruiting Number Girl drummer Ahito Inazawa, guitarist So Yoshikane and former Art-School bassist Hidekazu Hinata, he set about expanding on the possibilities suggested by his previous band's final album, "Num-Heavymetallic." While not entirely shucking the Number Girl sound, he made it a whole lot weirder, broadening the palate to include fiddly math rock and the influence of Prince and Public Enemy. Live, their songs spin off into lengthy improvised segments before suddenly kicking back in with another burst of razor-sharp riffage.