‘Japanese movies are too long” is a comment I’ve heard many times over the years. In fact, one Asian film reviewer of my acquaintance writes “(J-film title) could be cut by (number of minutes)” so often that he’s probably made it into a keyboard shortcut.

Japanese directors have also turned in some excellent long films, however, from Akira Kurosawa’s “Shichinin no Samurai” (“Seven Samurai,” 207 minutes) to Sion Sono’s “Ai no Mukidashi” (“Love Exposure,” 237 minutes). Even so, I quailed when I saw the running time of “Happy Hour,” Ryusuke Hamaguchi’s female friendship drama: 317 minutes. That is a long sit by any standard.

But its four female leads, unknowns all, received a collective best actress prize at this year’s Locarno International Film Festival, while the script by Hamaguchi and his two co-writers was given a special mention. The film has since been invited to festivals in Vienna, London and San Diego. Deservedly so: “Happy Hour” engages rather than exhausts with its length and complexity.

Despite such standard J-drama tropes as convenient coincidences and stormy exits, the film’s story develops organically from its core relationships, not its plot devices. And its four principals grapple realistically with universal questions: How can I love? Who can I trust? When should I leave?

Cast entirely from participants in acting workshops Hamaguchi taught while an artist in residence at Design and Creative Center Kobe (KIITO), the film has its share of amateurish moments, but even its more awkward actors convey a feeling of emotional honesty, as though they are living their lines, not just delivering them.

The four friends at the story’s center are: Akari (Sachie Tanaka), a hardworking nurse who is currently unattached; Fumi (Maiko Mihara), a stressed PR rep married to a sober-sided book editor; Sakurako (Hazuki Kikuchi), a harried housewife with a sullen teenage son, controlling husband and opinionated mother-in-law: and Jun (Rira Kawamura), a self-described “ex-housewife” in the process of divorcing her straight-arrow scientist husband.

One obvious parallel is the HBO hit “Sex and the City,” but the resemblance between the American show’s quartet of high-living Manhattanites and the hard-pressed foursome of the ironically titled “Happy Hour” does not extend much further beyond their enjoyment of each other’s company.

Even that is threatened when Akari and Fumi realize that Jun was keeping her divorce a secret between her and Sakurako, a friend since their school days. “If you lie, we can’t be friends,” Akari tells Sakurako bluntly. Meanwhile, Jun’s husband, Yohei, stubbornly refuses to give her up, even after she tells the divorce court judge that their nearly silent marriage was killing her spirit. Then, with no explanation to anyone, Jun disappears.

Other complications arise, most having to do with issues of trust and communication between friends, spouses and family members — issues that fester under the surface of everyday banalities and untruths but eventually erupt with consequences unforeseeable.

Hamaguchi, who developed the script in collaboration with his actors and shot the film over a period of eight months, tells this story with a seemingly formless naturalism, while artfully structuring it with simple but powerful metaphors and motifs.

One appears early on at a communications workshop attended by the four friends and taught by a charismatic, if manipulative, artist. He instructs the participants to press an ear against a partner’s solar plexus to not only hear digestive rumblings but feel the other person’s existential reality.

The ultimate purpose is to break through the isolation of modern life and create bonds beyond social roles and rules. To their credit, the women struggle to keep those bonds alive, even as they are being tested to the limit. That’s what friends are for, isn’t it?