Between its listing in the Glasgow Film Festival programme and the title provided by its UK distributors All the Anime, there’s some confusion as to the correct name of the directorial debut from Mari Okada, the award winning screenwriter whose previous work includes The Anthem of the Heart, cult favourite television series anohana: The Flower We Saw That Day and nearly fifty other television projects. Our tickets read “Let’s Decorate the Promised Flowers in the Farewell Morning”, presumably a clumsy direct translation of its original Japanese title, while the film’s opening credits offer “Maquia: When the Promised Flower Blooms”. Let’s face it; neither screams box-office sensation, and these names are only a taste of the film’s myriad other barriers to mainstream legibility. Which is a shame, because The Promised Flower (let’s go with that for now) sports themes both fit for and worthy of widespread recognition.

Maquia, it turns out, is the name of the protagonist, a young member of a species of angelic beings called the Iolph. It’s difficult to digest who exactly the Iolph are in a single viewing, what with various capitalised fantasy jargon terms to keep track of, but the important thing to know is that they age at a much slower rate than humans. Maquia may have the appearance of fifteen-year-old girl, but she’s actually many times older. The Iolph are a race of weavers who spend their days fashioning the Hibiol, the celestial cloth which measures the passage of time. As a certain Time Lord will tell you, being a custodian of the universe’s clock is a considerable burden to bear, and it’s Maquia’s coming to terms with this responsibility that frames the events of the film.

Like the oft-quoted metaphor about ships in the nighttime, we humans all pass each other on our way in and out of this world, our timelines irreparably out of sync. For Maquia and the other Iolph however, things work differently. A human lifetime is fairly insubstantial in Iolph years, making Maquia’s plight a similar one to the aforementioned Doctor’s or Jim Jarmusch’s vampire couple in Only Lovers Left Alive. Mixing with humans, Maquia is warned at the film’s outset, is recipe for loneliness. We know how these stories go.

And yet, while The Promised Flower tells a familiar story about love in impossible circumstances, it isn’t concerned romantic love. Instead, the film is an emphatic and impassioned ode to motherhood, one which surely reflects Okada’s feelings about what her own mother must have gone through as a single parent.

After an invasion involving ancient dragons is carried out upon the Iolph kingdom, Maquia is flung from her sky-hung home and into the human realm where she encounters an orphaned baby boy, his parents victims of an ongoing conflict between the terrestrial nations. She names him Erial, and the remainder of the film depicts the boy’s growth. The pair are taken in by Mido, another single mother with two children of her own, and it’s here that the film establishes its theme of motherhood as an essential thread holding life together across time, much like the Iolph’s Hibiol cloth. Maquia returns to Mido’s advice time and again throughout her journey, and it’s in this way that we see how life is nurtured across generations in the advice and experience of one woman passed down to another.

As a mother that never ages, Maquia herself becomes a sort of symbol for the experience of a parent and all the joys and struggles that come with it. Through her we see Erial grow from cute toddler to despondent teenager and distant young adult. We feel her dismay when the child she’s dedicated herself entirely to eventually pushes her away, resigned to forging his own path. The transformation of the film’s stunning and eccentric fantasy setting reflect Maquia’s accelerated perception of human time, the world evolving from a medieval period into steampunk-esque industrial age at a disconcerting pace.

The film’s fantasy elements serve it best when they carry on quietly in the background like this, teasing the viewer’s imagination without overpowering the central relationship between Maquia and Erial. But too often the film engages in the kind of convoluted worldbuilding that mars much genre fiction, ticking all the usual boxes: ancient beings; royal lineages; long-standing conflicts. The result is two hour film which feels twice as long, dense with plot detail that ultimately doesn’t matter add much to the mother and child story at its centre. The opening twenty minutes is particularly disorienting, plunging the viewer straight into the surreal Iolph world and right back out again before they can as much as wrap their head around these odd beings and their history. Anime fans are used to this sort of lore-dumping of course, but there’s a real risk of a more general audience being alienated by all the gobbledygook, which would be a shame given the universal appeal of its themes and story.

In terms of pure emotional impact, The Promised Flower is a triumph. Touching and thoroughly imaginative, Mari Okada’s first feature film offers a welcomely sentimental celebration of motherhood which is rare in cinema in general, nevermind anime. It’s bloated and a little over-thought, perhaps to the point, unfortunately, of turning off more casual film viewers. But those who stick with it are in for a moving, memorable experience.

Maquia: When The Promised Flower Blooms will have a limited release in the UK in June 2018.