So yes, Maruyama is indeed a middle schooler and yes, the driving force in his life is a dream to reach his penis with his tongue. To this end he performs daily stretches, experiments with different positions and even joins the school wrestling team. Why the odd obsession? As the narrator says, "to know that, you'd have to ask a fourteen-year-old boy."
Maruyama, we learn, is also prone to fantasy, to the point where he often mistakes his imaginary experiences for reality. The audience is of course, invited to partake in these fantasy sequences, which usually strike an odd balance between Michel Gondry's sensitive whimsy and a Japanese Girls Gone Wild video. But honestly, that's probably about right for a fourteen-year-old kid with an overactive imagination.
However, rather than focusing exclusively on Maruyama, the film plays as more of an ensemble comedy set in the community housing project where the boy lives. Its consistently hilarious and oddly touching subplots involve everyone from an old man with dementia to Maruyama's soap-opera obsessed mom, to a new, clumsy neighbor who may or may not be a mass murderer. Just like the central plot, each one of these could have played like episodic sketch comedy, but Hokudo invests everything with wit, humanity and charmingly off-kilter comic timing. The film jumps between all of them with verve and style, and the end result is a crude, post-modern version of Ozu's comedies like Good Morning, or a spry, more energetic cousin to The Taste of Tea.
The film does, alas finally lose steam when Maruyama's fantasies completely take over the film during the climax. Unlike the earlier, more imaginative fantasy sequences, almost all of these involve superheros and guns. I suppose this is realistic, given that we're dealing with a fourteen-year-old boy, but it means that rather than witty and unexpected resolution to all of the story-threads, we're simply treated to the same wacky shoot-em-up action scenes that have been done in a million other modern Japanese films.
It's disappointing, but by that point, the movie has earned more than enough good will to coast for a bit and provided several show-stopping comic scenes, one of which includes the coolest Japanese rock song of the year. Sure it would have been nice if Kudo had wrapped it all up about 20 minutes earlier and taken a bow, but on the other hand, I suspect that his young protagonist would have had some harsh words about that decision. After all, if you're going to make a film about going for the gusto, you'd better go for it yourself too.