'Parade'

How much do we really know about anyone? This thought, the basis of many a paranoid delusion, is grounded in a human fact: We are all locked inside our own heads, communicating only a small fraction of our thoughts and feelings to others, when we are not actively misrepresenting them.

But for the characters in Isao Yukisada’s ensemble drama “Parade,” the love and trust that are the surest escapes from our isolation are in short supply.

Based on a novel by Shuichi Yoshida, the film begins with a setup for a “Friends”-like sitcom: Four 20-somethings share a cramped apartment in urban Tokyo. Strangers before they moved in, they are casually familiar, but not really close. Also, they are distinctly different in personality and outlook.

Naoki (Tatsuya Fujiwara) has been living in the apartment the longest. To sweat off stress from his job at a film distribution company, he jogs for hours around the neighborhood, but is still tightly wound. Mirai (Karina), a struggling commercial illustrator, smokes like a chimney, regularly drinks herself blotto at a local gay bar and affects a cynical, know-it-all attitude. Kotomi (Shihori Kanjiya), a chirpy-but-sad unemployed actress, is carrying on a pathetically one-sided affair with a self-obsessed TV drama heartthrob. The youngest, 21-year-old Ryosuke (Keisuke Koide), is a loud, callow college student awkward in love with a self-assured older classmate.

Yukisada, a director of commercial melodramas for much of the past decade (“Closed Note,” “Sekai no Chushin de Ai o Sakebu”), has returned to his indie roots for this film. It is especially reminiscent of his 1998 debut, “Open House,” which is also about wrestling with loneliness and isolation in the big city — and taking in a cute stranger as one would a stray cat.

In “Parade” that stranger is Satoru (Kento Hayashi), a feral blond teenager who insinuates himself into the apartment — until the housemates realize that no one really knows him. They at first suspect him of being a thief, but he tells them a dead drunk Mirai invited him in — an incident the abashed Mirai no longer remembers.

Satoru has the charm and wiles of a street kid who has mastered all the survival tricks, including the selling of his body to middle-aged men. He is soon accepted by the quartet — if not quite trusted.

Meanwhile, Ryosuke and Kotomi are scheming to learn why dodgy-looking men, including a famous politician (Renji Ishibashi), are always in and out of the apartment next door. Are they patronizing a prostitute?

Then Mirai comes across a police flyer asking for information about a serial killer who is terrorizing the neighborhood. Can Satoru be the one, she wonders? But instead of calling the cops, she goes with him to a nearby amusement park at night to ride the merry-go-round — and confide.

Naoki, however, is not so trusting. One day he tails Satoru to learn what he’s hiding.

Satoru is not the only one leading a secret life, though; everyone in the apartment is. But do the false fronts matter? As Mirai notes, housemates are like posters on Internet message boards or chat rooms. “If you don’t like it, you can go,” she says. “If you want to stay, you’d better just smile.” That is, turn a blind eye — and keep your heart locked.

Yukisada, who also wrote the script, works out the implications of that statement with a sure-footed narrative logic that only looks amorphous and indirect. That is, instead of circling around his subject and gently leading us to a downer epiphany — i.e., we are all alone — he is stealthily setting us up for a wallop.

Some will leave the film feeling sucker-punched — and I don’t blame them. I wasn’t quite sold on the final twists either. At the same time, the film points to something real and dark in human nature: Our limitless ability to adapt, like the villagers in Nazi-ruled Europe who celebrated local festivals while smoke wafted over from nearby crematoriums.

Extreme? But so, finally, is the film, though it’s hard to call it a shocker in the usual sense. Instead of monsters lunging out, ordinary people try get on with their ordinary lives. But the meaning of “ordinary,” “Parade” argues, has changed — and that is the scariest thing of all.