The opening scenes establish the unforced style of Nobody Knows, a heart-rending film by Japanese director Hirokazu Kore-eda about four Tokyo youngsters who are abandoned by their mother. The mother (played by the actress You) appears before a new landlord in the company of her sober, alert-eyed 12-year-old son Akira (Yûya Yagira); gift in hand, she explains with engaging self-effacement that they’re alone and that she hopes they can count on the couple to watch out for them.

It’s a routine she’s perfected. What she’s really doing is purchasing the landlords’ unwitting complicity—that is, their remoteness—by assuring them that she’s respectable and won’t be any trouble. Meanwhile Akira’s youngest siblings, Shigeru (Hiei Kimura) and Yuki (Momoko Shimizu), are packed away in the luggage, and Kyoko (Ayu Kitaura), the second oldest, is waiting at the bus station for Akira so he can sneak her into the apartment.

The mother schemes to keep all four children in the two-bedroom space. She hides the truth from the landlords by permitting only Akira to go out during the day, while she’s at work. It’s his job to buy groceries and whatever items they can afford to keep Shigeru and Yuki from getting bored. Kyoko, who is mature enough to be trusted with a clandestine task, steals onto the balcony to do the laundry.

Our impulse to be appalled at the deprivation the children suffer—Akira is out of school, the others are closeted from the outside world—is at first tempered somewhat by our fascination with the family’s deftness in managing this lifestyle. And we note the mother’s loving attentiveness to each of the kids when she comes home at the end of the day. But she’s rather childlike herself; she speaks in a tinkling, breathy voice (a little like the voice of the American actress Jennifer Tilly, who specializes in playing baby-doll women). She seems to stay away later and later into the evening; one night she arrives home drunk.

By the time she’s confided in Akira that she’s hoping her boyfriend will adopt all of them—though she hasn’t yet told him that she’s got kids—we’re prepared for the day when she doesn’t come home at all. She leaves a note and an envelope of money for Akira, who has to work out how to survive. (He taps a couple of her old boyfriends, who may or may not be the fathers of his siblings, for whatever he can get out of them; he befriends a clerk at a local store, who slips him food.) She returns once; another time, she sends money. Then she’s gone, presumably forever.

Though the narrative bears some resemblances to the famous young-adult novel Flowers in the Attic, by V. C. Andrews, it’s based on a true story, and whereas Andrews’s book is lurid and baroque, Kore-eda’s approach is the opposite. He accumulates details subtly but inexorably. He has an unmelodramatic way of showing the escalating dilapidation of the apartment—Akira isn’t able to pay the water and electricity bills—and the increasing raggedness of the children. He’s trying for the neo-realist style, that is, realism grounded in a carefully rendered social and economic reality, as in such classic films about children as Vittorio De Sica’s Shoeshine, Luis Buñuel’s Los Olvidados and Satyajit Ray’s Aparajito.

There’s much to admire in Kore-eda’s workmanship and restraint. The problem is that he’s more of a reporter than a dramatist. Unlike DeSica and others, Kore-eda isn’t a lyrical director. The story has a clear arc, yet the movie feels shapeless. The young performers (including Hanae Kan as a schoolgirl who befriends Akira and becomes an adjunct member of the family) are observant and convincing but not especially expressive; in most of the scenes, you project the emotions implied by the meticulously contrived scenario.

There’s one lovely moment when Akira takes little Yuki out as a treat for her birthday. They watch the monorail that travels to the airport, and Akira promises her that someday he’ll show her the planes. And there’s a remarkable scene in which Shigeru runs off and Akira finds him playing with some other boys in the street; he’s furious—not because his kid brother has broken the rules, but because he’s enjoying a simple childhood pleasure that Akira himself has been denied. Nobody Knows could have used more of these stirring sequences.