So, we're treading on spoiler eggshells (but so is the title, and so are the ads). Fukada introduces us to a typical nuclear-family micro-unit: Dad Toshio (Kanji Furutachi) is an inattentive machinist working his own shop. Mom Akie (Mariko Tsutsui) is a tense, vocally Christian helicopter-er, hovering over their young daughter, Notaru (Kana Mahiro), who's learning a school piece on their clunky harmonium. The clacking beat of the girl's metronome suggests a life of forced order, and Fukada paces his scenes exactly that way — without momentum or variation. The strategy doesn't lull us so much as it tunes our ultrasounds for tiny cracks in the façade — mostly from Tsutsui. Anxious and unpretty, Akie can't hide her pious yet paranoid discomfort with just about everybody, including her little girl.
The break in the rhythm: Yasaka (the great Tadanobu Asano, older but still supercool), an overly polite, buttoned-down mystery man in white, and an old friend of Toshio's fresh out of prison. Immediately, much to Akie's chagrin, Yasaka is given a shop job and a room. From there we watch the obsequious Yasaka charm both mother and daughter, in a low-key, James M. Cain style that will surprise no one.
But then the truth beneath all of this repressed politesse sprouts, and Harmonium turns into a methodical cascade of very bad things, compounded by lust and guilt and retribution and tumbling out over years. Fukada's cautious visual tone doesn't really change, but the characters do, twisting under pressure and closing in on madness. There are base ingredients from Kiyoshi Kurosawa and Park Chan-wook in the mix, but Fukada's register is decidedly unsensational, even secretive. The simple appearance of a family-snapshot selfie, eight years later and impossibly printed from the wrong person's phone, evokes a dark half of the movie that we don't ever see.
Just as in the best old-school, Cain-style noir, Fukada's film is eloquent about the fragile privileges of modern urban life and the hidden lies it can be built upon. (The stranger-comes-to-town blueprint has always been more about the town than about the stranger.) Asano has been one of modern movies' grooviest exponents at least since he disrupted the samurai code with gay desire in Nagisa Oshima's Gohatto 18 years ago, but the star here is really Tsutsui, who lays herself subtly bare as this nervous and discontented wife ages and grows fearsomely neurotic over an eight-year span, weathering tragedies we see and shameful betrayals we don't. When she finally decides to close the book on the family's future, it feels inevitable.