Which shapes a child more, nature or nurture? Many Americans would pick the latter, optimistically convinced that kids come to resemble those who raise them in the ways that matter most. For the parents in this Japanese drama from writer-director Hirokazu Koreeda, however, the question isn't abstract. They've just discovered that their 6-year-old son isn't genetically theirs.

Architect Ryota Nonomiya (Masaharu Fukuyama) has been raising young Keita (Keita Ninomiya) to be an achiever like his dad, giving him private school, piano lessons and lectures on the virtues of competition. He's dismayed by the boy's "kindness," but attributes it to his more easygoing mom, Midori (Machiko Ono).

Then unlikely news comes from the hospital where Keita was born: The Nonomiyas' son was switched at birth. These impeccably groomed professionals have been raising the offspring of a loud, boisterous couple (Yôko Maki and Rirî Furankî) who own a rickety electronics store and exercise a chaos-friendly parenting style. Two very different families face the same choice: Should they continue to raise their unwittingly adopted child, or exchange him for a biological offspring who's an unknown quantity?

Hospital administrators urge the couples to make the switch. Without openly defying these authorities, three of the parents drag their feet, clearly preferring the status quo. The exception is Ryota, who sees fatherhood as a matter of bloodline. Has he been wasting his efforts on a kid who'll never amount to more than the son of a shopkeeper?

It's no surprise that Steven Spielberg scooped up remake rights to Like Father, Like Son after he saw the film at Cannes, where it won the Jury Prize. The story evokes old-school Hollywood "issue" dramas like Kramer vs. Kramer. And Ryota is a character type with whom American moviegoers are all too familiar: The workaholic who needs to Learn a Lesson about spending more time with his family.

In the wrong hands, this would have been a syrupy tale about the intangible bonds between parent and child. But Koreeda, the acclaimed maker of several films showcasing children (including I Wish and Nobody Knows), gives it a brisk lightness. Under his direction, child actors never play "cute," and low-key personalities get as much attention as big ones. As a result, the bond between Keita and Midori — both openly submissive to Ryota, yet secretly pitting their love against him — comes through with heartbreaking clarity. And, while Ryota does experience the evolution you'd expect — with a few clumsy transitional scenes — he also emerges as a three-dimensional character with reasons for his cruelty.

Koreeda uses light and space to show us what the generally subtle dialogue doesn't tell us: We learn plenty from the impersonal modernism of the hospital, the hotel-like blandness of the Nonomiyas' apartment and the happy clutter in which the other family lives. This is a film where details count: When Ryota spots his biological son chewing a drinking straw, his displeasure is palpable.

Like Father doesn't answer the nature-versus-nurture question, nor does it need to. The real question is simpler: How attached do parents feel after six years with a child? Is a DNA test enough to make them let go?

By the time you read this, Like Father, Like Son may have left our screens. (Look for it on video in May.) But March 14 brings another powerful Japanese film to Vermont: Hayao Miyazaki's animated passion project The Wind Rises. This fictionalized biography of engineer Jiro Horikoshi lost the Best Animated Feature Oscar to Disney's Frozen, but they aren't comparable: Miyazaki's film is hand-drawn and adult oriented. The director has received flack for not being more explicit about the horrific consequences of Horikoshi's ambition: He designed the Zero fighters that killed so many Allies in World War II. But few would dispute that The Wind Rises is a mind-bendingly gorgeous film.