Attention to detail is one thing we typically celebrate in a cinematic period piece, a movie meant to transport us to a particular corner of the past. But when it comes to the Edo Period Japanese romance “Okiku and the World (Sekai no Okiku),” we acknowledge the limits of such celebrating.

This mostly black and white drama is “Seven Samurai” serious, right down to the scent. A tale of a samurai’s daughter’s attraction to a manure man, you can almost smell the excrement, recreated in diarrhetic detail, right down to the texture.

Writer-director Junji Sakamoto’s 19th century parable is about the real “circle of life” — eat, excrete, fertilize food to eat, repeat — and how that relates to people and class near the end of “feudal” Japan. Shoguns ruled through samurai, schools were run by Buddhist sects and in or outside of those classes, everybody was locked in a world of feces.

That’s what Yasuke (Sôsuke Ikematsu) traffics in. He is recognized by his “stink,” tolerated and accepted within his world, because everybody needs to hit the outhouse on a regular basis. The cesspool needs to be cleaned, and money changes hands — although not necessarily directly “hand to hand.” “Washing” those hands doesn’t go nearly far enough.

Feces, which one and all more bluntly label as “sh*t,” is a going concern (ahem) in an isolated culture lacking other sources of fertilizer. Yasuke buys and hauls, on foot and boat, human waste from temple toilets, tenement outhouses and samurai mansion sh*tters and delivers it for sale to farms on the outskirts of pre-Tokyo Edo.

One and all may look down on Yasuke. But when we meet him, he’s not having that from young Chuji (Kan’ichirô Satô), who collects and sells scrap paper for recycling. He can’t support himself on that, and Yasuke quickly talks him into becoming his new partner. Because his old partner’s sick.

Scooping, toting, storing and spreading human waste is a good way to get sick. A lot.

The two are at their most delicate when they’re stuck in the rain at an outhouse where teacher Okiku (Haru Karoki) takes shelter.

If she has to “go,” they’ll leave. Oh no no, it’s raining, she insists (in Japanese). She’s just taking shelter like you guys. Well, OK. Yes yes. I DO have to. Please PLEASE go.

The humor here never quite descends into the juvenile. But when “poop” is not just your business, but everybody’s business — “We’re SAMURAI! We eat better! Our sh*t is WORTH MORE!” — one and all can have their junior high school sense of humor moments about it.

Okiku is the daughter of an ostracized samurai and any attraction she feels for a kindly manure man will have to transcend more than mere scent.

But as the two dung dealers collect, store — “Just like miso paste, sh*t’s better if you let it age a little.” — and spread their wares, Okiku faces tragedy and the loss of her father (Kôichi Satô) and her voice. The lowly manure men are destined to play a bigger role in her life, if she’s fated to survive and carry on.

Writer-director Sakamoto pays homage to the films of Kurosawa, especially “Rashomon,” in his ode to excrement. Compositions, settings and even the opening scene in the rain intentionally bring that film to mind.

This world is grim, Medieval black and white — sparing us endless sights of crap in living color. But as tiny glimpses of hope and romance are woven in, scenes shift to color, the best way to appreciate Okiku, her pink kimono and her slim hopes for a better life.

Sakamoto needlessly and tediously breaks Okiku’s story into “chapters,” which do little to distract us from the main thrust of the film — waste, not wasting waste and finding the zen nobility in even the lowliest labor and most easily discarded lives.

The world Sakamoto brings back to life — tenements where the residents gripe about the landlord’s more private and thus less likely to overflow in the rain toilet, tale telling told to ease bowel movements, classist bullying met with laughter — and flinging feces — is as vivid as any saga of samurai, shoguns, ronin and clans.

Because at the end of the day, the basest of human needs is not just a great fertilizer. It’s the greatest equalizer.

Rating: unrated, scatological humor, profanity

Cast: Haru Karoki, Kan’ichirô Satô, Sôsuke Ikematsu and Kôichi Satô

Credits: Scripted and directed by Junji Sakamoto. A Film Movement+ release.

Running time: 1:30