The “comedy of manners” is a long-established tradition of Western fiction. Jane Austen collected a lot of posthumous Oscars mastering that genre.

The “tragedy of manners” is less common, limited to the occasional “Remains of the Day.” But if any culture has the potential to claim it as its own, it might be Japan’s. A nation of rigid social norms and manners rendered into rituals, it’s fertile ground for Japanese fiction writers and filmmakers.

“True Mothers” is a long, somber Japanese tragedy about childbirth and adoption, and an object lesson in apology culture. Characters are wronged and do wrong, disappoint and let each other down. And nothing can be done about it and no one can move on with his or her life until that apology comes.

Filmmaker Naomi Kawase (“Sweet Bean”), adapting a novel by Mizuki Tsujimura, tells us two mothers and one child, breaking each story out separately in two long flashbacks, tying the women at a couple of intersections in their stories.

We meet doting mom Satoko (Hiromi Nagasaku) as she quietly sings to her little boy Asato (Reo Sato), who is brushing his teeth. It’s his first day of kindergarten, and she and husband Kiyokazu (Arata Iura) have planned their day around walking him to school.

She’s a stay-at-home mom, he’s a watch-checking office drone. But they’re a team and this kid, in his suspenders and cap, will have every advantage they can give them.

A call from the school later that same day interrupts that. There was a playground accident. Asato is blamed for it. He denies it, but Mom broods and frets over who to believe, how to gently question the teachers. She even calls the mother of the other little boy.

The woman she calls is taken aback that she hasn’t called to apologize, and dumps a blunt “settlement” demand, doubling down on her rudeness. An apology might fix this, but is it merited?

As she ponders this, Satoko takes us back to her courtship and the difficulties she and Kiyokazu had getting pregnant. He frets about this in a drunken bar confession with a colleague, professes to be less “obsessed” with having children, and even goes so far as suggest “divorce is an option,” offering her a way out. It’s a medical problem on his end and he feels humiliated.

They reluctantly turn to adoption, dealing with some fairly draconian conditions that “Baby Baton” demands — one spouse will have to give up their career, the child must be told he or she is adopted, etc.

After all that, now they have the added shame of wondering if their is pushing other kids off the monkey bars? To top it all, Satoko has been fielding with hang-up calls. Finally, the caller speaks and she says she’s the birth mother and she wants her child back.

That points us to the sadder story of teenaged Hikari (Aju Makita), a shy Nara schoolgirl who fell for the first guy to take an interest in her, swooned at her first kisses and wound up pregnant, to her family’s eternal shame.

Well, at least the boy apologized. But that’s perhaps the last thing that goes right for her.

Kawase and her players tell these interfolding stories with great sympathy and compassion, leaving little twists and bits of mystery for the viewer to pick up on as we’re immersed in lives that are tested by this pregnancy, this childhood and the ongoing repercussions of giving up a baby for adoption.

With Japan’s sagging birthrate, “True Mothers” has greater cultural significance at home than it does abroad. But the universal elements of this story are touching, no matter where you live.

The sedate, baby-steps storytelling style won’t be to every taste. “True Mothers” is a melodrama with 90 minutes of story awash in 139 minutes of movie.

Kawase holds our interest by letting us see the unexpressed pain of characters generally too well-mannered to express loss, shock, outrage and resentment out loud. That won’t entertain everyone who meets these “True Mothers,” but there it is.

MPAA Rating: unrated, adult subject matter

Cast: Hiromi Nagasaku, Arata Iura, Aju Makita and Reo Sato

Credits: Directed by Naomi Kawase, script by Naomi Kawase and Izumi Takahashi, based on a novel by Mizuki Tsujimura. A Film Movement Release.

Running time: 2:19