Warning: Spoilers ahead.
A group of American fourth-graders, led by perky Scarlett Johansson, travels to Tokyo to participate in an international karaoke contest. Jack Black turns in a feral performance as their coach, exhorting them to “stick it to Japan.” Bill Murray plays a wealthy ex-karaoke star who has lost all interest in karaoke and has been prevailed on, for an enormous fee, to serve as a judge. Murray, in a stunning departure from his last eighteen movies, is care-worn and worldly-wise. He encounters Black in the hotel bar and finds his infectious enthusiasm for karaoke grating at first. Eventually he completely fails to be won over.
The children, meanwhile, are left to explore Tokyo on their own. Johansson, in her schoool uniform, encounters a sarariman who proposes a little enjo-kosai, leading to a series of amusing misadventures and panty shots. Joey Gaydos, as gloomy but talented Zack, wanders down to the hotel bar and runs into Murray, who gets him drunk on sake and prevails on him to lead the patrons in a stirring rendition of “Devil With a Blue Dress On.” Other children are bowed to by the hotel’s staff, and bow back, giggling.
Black does his best with Murray, but the children still lose the contest to the reigning Japanese karaoke champions. They return to America sadder but wiser, having learned from Murray that there are more important things in life than winning, such as raking in huge appearance fees.
Jack Black and Bill Murray, despite the smoldering sexual tension between them, do not actually have sex.