Grade: A-

If one were hard-hearted, he might dismiss Hirokazu Kore-eda’s “Nobody Knows” as a two-and-a-half hour Japanese “Home Alone” without the slapstick. That wouldn’t be a fair synopsis, but it’s not an entirely inaccurate one either. The script, loosely based on a incident that occurred in 1988, involves four young children, aged twelve through four, who are effectively abandoned in a dingy apartment by their flighty mother Keiko (You), who’s only just acquired the place by telling the landlords she has just one son. She leaves a note behind asking the oldest, the somewhat dour and studious Akira (Yuya Yagira), to look after his half-brother and two half-sisters, ten-year old Kyoko (Ayu Kitaura), a solemn child who takes over many of the household duties while dreaming of taking piano lessons; seven-year old Shigeru (Hiei Kimura), whose natural impetuosity is stifled by the need to remain hidden indoors; and the baby of the family, four-year old Yuki (Momoko Shimizu), who’s become accustomed to being transported secretly inside suitcases. Keiko, who claims to be away on unspecified job-related business, does leave some cash behind, and at one point briefly returns bearing little gifts, but she’s soon off again.

Adults, in fact, play marginal roles in “Nobody Knows” from the very beginning. Keiko is on scene only sporadically, the landlords are blissfully unaware of what’s going on and but slightly concerned in any event, and when Akira visits the various fathers of the children for handouts as the money from his mother dries up, they offer excuses rather than help. In fact, the only person who shows any real sympathy is another child, a well-off student named Suki (Hanae Kan), who’s unhappy at school and cuts class regularly. But she can do little more than commiserate and watch as the siblings struggle to survive on their own.

That struggle is the heart and soul of Kore-eda’s remarkable film, which depicts both the heartbreak and the resiliency of childhood in a fashion that rivals that of Charles Laughton’s “The Night of the Hunter”–but in a style that’s naturalistic rather than expressionistic. (And, of course, there’s no fairy-godmother like figure who appears like a dea ex machina to save the day.) “Nobody Knows” is in effect a chronicle of Akira’s efforts to meet his responsibilities as head of his little family in the face of mounting financial problems and disorder in the unkempt flat, which eventually has its water and electricity turned off for lack of payment. At the same time the boy feels a longing for comradeship and a chance simply to have some childish fun–a desire shown not only in his friendship with Suki and a short-lived connection with a couple of video-game-loving schoolboys but also in an episode when he’s tapped by a kids’ baseball coach to join the team, which happens to be momentarily short-handed.

What’s really moving about “Nobody Knows” is that it never descends to maudlin sentimentality, despite the constant invitation to do so. Kore-eda shoots the film in a stark, almost documentary style without, however, italicizing the grimness of the situation in a heavy-handed way; there’s no more false grittiness in his approach than there is false romanticism. Even a tragedy toward the close isn’t milked for tears, and the almost gentle matter-of-factness, touched by only a hint of melancholy, proves more powerful than a more overt attitude would have been. But the director’s sensitivity would have meant little were it not for the amazing performance of Yagira. The boy, who actually ages over the course of the picture (which was shot across a full year), perfectly captures both Akira’s essential seriousness and his pre-teen desire for simple abandon. It’s a wonderfully understated and astonishingly real turn. The rest of the cast is fine down the line, with the other siblings especially well drawn, but all are basically supportive to Yagira, who carries the film as much as Akira carries his family. From the purely visual perspective “Nobody Knows” has a deceptively unvarnished look–taken together Yutaka Yamazaki’s cinematography and Toshihiro Isomi and Keiko Mitsumatsu’s art direction create a kind of luminous plainness–a extraordinarily combination that characterizes the entire film.

As narrative, “Nobody Knows” trails off rather than ending. There’s effectively no resolution here, apart from the final observation that nothing can crush these children’s drive to keep going, and one may justifiably be left wondering how, from a purely practical standpoint, they can do so. That’s at once heart-warming and heart-rending, though in a delicate rather than overbearing way. And it’s also deeply troubling from a social and political perspective, though that’s something the picture never overtly proclaims. Would that more pictures had a similar sense of subtlety and restraint, which in the final analysis proves much more compelling than the strident, self-congratulatory treatment such socially conscious stories ordinarily receive.