There is more than one kind of Japanese movie, but to watch Tarantino films and follow the fan-boy Web sites, one would think that Japan is awash in anime pyrotechnics, gruesome violence and sex with minors. But even as Hirokazu Kore-eda’s quietly enthralling Nobody Knows contains a doughty young boy hero with the all-Nipponese name of Akira and a supporting character of a Japanese schoolgirl in the so-eroticized navy and white uniform and knee socks, this clear-eyed and unsentimental film operates on an often breathtakingly realist plane. Nobody Knows is a title that refers to the obliviousness of the inhabitants of a Tokyo neighborhood to a social tragedy unfolding in their midst. People in the neighborhood may cluck disapprovingly at the four unkempt young children scurrying in the streets and doing their laundry in a public park. They may avert their eyes and wonder just where the children’s parents are. But what nobody knows is that these four children, headed by Akira, the oldest, have been abandoned by their mother and are struggling to survive on their own in their apartment. But the title of the film is supremely ironic, because it’s not quite true. Those who encounter the children are well aware that there is something terribly wrong, but most choose not to get involved. There are also a couple of sympathetic outsiders who are in on the secret and who offer assistance.

In short, everybody knows what is going on with these children, and this, of course, includes those of us in the audience. Throughout this film, we’re privy to the extraordinary relationship Hirokazu and his film crew established built with an exceptional quartet of young children, kids that he cast through nontraditional auditioning methods.

Our unease begins almost immediately when we meet a bubbly but clearly scatterbrained woman named Keiko as she and her oldest child arrive at a new apartment. There’s something too insistent about the way she introduces Akira to the landlords. Moments later, when they’re inside the apartment, Keiko and Akira open the two heavy suitcases they’ve lugged up the stairs. Inside the suitcases are two younger children. A fourth child, a shy and serious girl named Kyoko, sneaks into the apartment later that night. We learn that the family is fatherless, and that Keiko is keeping her children secretly and illegally in a too-small apartment. To keep up this fiction, the three younger children are forbidden to go outdoors; Akira, the oldest, is her only official child and as such is the only one permitted to leave the apartment.

We don’t learn much about Keiko except that she has a humble factory job and has fathered her children by several unreliable men. Played by a cheerful and benign Japanese television personality known as You, Keiko is little more than a child herself. Though she loves her children, her determined quest for Mr. Right takes her on longer and longer trips away from her children. Finally, she doesn’t return.

The rest of the film is taken up with the six-month ordeal of her children as 12-year-old Akira struggles to support his younger siblings. Quickly running out of the money Keiko has left, Akira begs from a sympathetic local deli and also makes the friendship of Saki, a schoolgirl his own age who is the unfortunate victim of a bullying campaign at her school. Although Saki mostly has just her friendship to offer, a serious conflict arises when she earns money by going on a date with a middle-aged man (this practice of teen prostitution, called enjo kosai, is a common, if frowned-upon, phenomenon in Japan). If there’s a false note in Nobody Knows, it may be Akira’s revulsion at Saki’s act of chaste prostitution. We’re told that Akira, like his siblings, has never been to school, and it seems unlikely that such an unsocialized and penniless boy would be so fastidious. Of course, he may have had a crush, but Hirokazu wisely skirts this obvious narrative option.

Hirokazu based his script on an infamous Japanese case from 1988, when it was discovered that four children, born of different fathers, were living alone in an apartment after being abandoned by their mother. A national scandal at the time, the case inspired Hirokazu and he nursed the desire to make a film about it all through the 1990s as he built his international reputation on quiet films of moral and spiritual inquiry like Maborosi and After Life, films that cut against the grain of contemporary Japanese pop cinema. After Life, his most recent local release, is a Wim Wenders-like imaginative excursion in which angel-like counselors work with the recently deceased to identify their single most cherished memories, the only ones they’ll be allowed to carry with them into the great beyond.

With Nobody Knows, Hirokazu returns to the temporal realm and employs documentary techniques to achieve an extraordinary level of intimacy with his child-actors. His actors were too young and inexperienced to act from a script, so Hirokazu instead created a dramatic framework and spent a year filming his charges. There’s very little dialogue between the children; instead, after the children became acclimated to the camera’s presence, he encouraged improvisation among them. Some of the most graceful scenes in the film clearly emerged from moments of unforced spontaneity among the kids. Distinct personalities take shape, but Hirokazu has also noted in interviews that the children are indeed acting–for example, the director reports that Kitaura Ayu, who plays the quiet and sensible Kyoko, possesses a vivacious personality completely at odds from her character.

For a film of fairly searing social realism, Nobody Knows eschews the finger-pointing of such realists as Loach and Sayles, instead becoming a remarkable feat of structured improvisation, a project that documents how the children adapt to the situation. Visually, too, Hirokazu’s images–achieved in mostly natural light on Super-16 stock–are luminous and captivating, putting to shame the apparently requisite grubbiness of social realism. In its easy familiarity with the child’s dreamlike point of view, Nobody Knows resembles Lynn Ramsey’s Ratcatcher, David Gordon Green’s George Washington or Edward Yang’s Yi-Yi. Augmenting the film’s lyricism is the Japanese pop duo Gontiti’s lovely and simple score, plucked on ukulele and guitar, and a song by chanteuse Tate Takako graces the film’s sad coda.

In recent years, Iranian films–particularly those of Kiarostami–have boldly incorporated spontaneous documentary elements into narrative filmmaking, but Nobody Knows doesn’t have the reassurance (or irritation) of a strong adult presence. Nobody Knows is also distinct from the improvised films of Mike Leigh, whose Life is Sweet, Naked and Vera Drake could only be possible with the collaboration of experienced stage actors with serious chops.

But film can be a marvelously liberating medium that levels distinctions between actors and non-actors. Last year’s Cannes jury was so impressed with the performance of neophyte actor Yagira Yuya as Akira that he won the best actor award. Indeed, Yuya displays remarkable screen charisma in a role that requires him to be alternately an adult and a child. His Akira is quite savvy with adults, establishing smart relationships and keeping food on his family’s table. But midway through the film, he also becomes a lonely boy who turns the apartment into an all-night Play Station party pad for local kids. And, in the course of the film, Yuya (and Akira) hit puberty, which the film dutifully dramatizes.

Nobody Knows finally stops short of being a work of social protest. Instead, it becomes something much more interesting: a meditation on the loneliness of crowds and how humans connect and fail to connect in the modern city. We understand how it is possible for young children or anyone else to live in such dire straits in a modern city, in plain sight. And we can only wonder why families don’t break down more often under the stress of urban living.