The Wind Rises is the saddest film of the year. The moment I realized this came about a quarter of the way through Japanese animator Hayao Miyazaki’s latest masterpiece. It is 1923, and Jiro Horikoshi, an aspiring airplane engineer, is traveling by steam train to Tokyo. Suddenly, the earth convulses, transforming the level tracks into an undulating rollercoaster. Plunging toward the trough of a shockwave, the engine screams to a halt. It is an earthquake.

Flames flicker on the horizon. The planet belches and groans. Passengers flee the locomotive, fearing an explosion. And then, as the tremors begin to subside, Miyazaki cuts to a close-up of the ground: gray pebbles, a green weed. For three seconds, maybe four, this is all we see and hear. The pebbles rattling together, then slowing and quieting, then becoming still and silent again. The earthquake—the deadliest in Japanese history—is over.

The Wind Rises is sad for several reasons. One is the story itself, which is partly a biography of Horikoshi, the pioneering Japanese engineer who designed the famous Mitsubishi A6M Zero World War II fighter plane, and partly an adaptation of Kaze Tachinu, a 1936-1937 novel about a young woman dying of tuberculosis. In Miyazaki’s movie, all Horikoshi wants “to do [is] to make something beautiful.” But when he falls in love with the doomed girl, he is faced with a tragic dilemma: pursuing his dream means endangering his wife and enabling the war. Horikoshi presses on regardless. His wife dies. The bombs fall.

Another reason The Wind Rises is so sad is that it seems to be a story about Miyazaki himself. The director’s mother suffered, like the movie’s ingenue, from tuberculosis, and his father, Katsuji Miyazaki, founded an aircraft company that manufactured parts, including rudders, for the Zero. Miyazaki has been obsessed with aviation ever since. The name he took for his legendary studio, ghibli, is a word Italian pilots once used to describe a wind blowing from the Sahara, and aviation figures heavily in several of his films, including Porco Rosso, which stars a porcine, anti-fascist pilot; Laputa: Castle in the Sky, which features ornithhopters flown by pirates; and My Neighbor Totoro, in which a surreal cat bus with headlight eyes soars through the sky.

In The Wind Rises, Horikoshi’s dream of designing a plane is a synecdoche for creativity itself—flight, like art, is an attempt to leave the earthbound world behind—and as a result the movie becomes a subtle allegory of Miyazaki’s life and concerns as an artist: the long hours, from 9:00 a.m. to 4:30 a.m., that he worked as an animator; the wife, Akemi Ota, he barely got to see; and the real-life pressures that can corrupt even the most well-meaning creation.

But the saddest thing about Miyazaki’s new film—the thing that struck me as those pebbles clattered on screen—is that it is probably his last. Miyazaki has announced his retirement before, notably after releasing Princess Mononoke in 1997. But on Sept. 6, he assured his fans that he was “quite serious” this time, adding that, at 72, animating had become too “strenuous” for him. Without Miyazaki, the world of children’s movies will be a much sadder place.

Miyazaki is often likened to Walt Disney, and on a superficial level, the comparison makes a certain kind of sense. Both began as cartoonists, transitioned into animation, and eventually founded their own studios. Both were visionaries who connected with generations of children and adults.

But while Disney graduated from the drafting table to the corner office, Miyazaki has always stayed in the trenches, writing, directing, storyboarding, and drawing the characters for all 11 of his films. He is perhaps our only children’s auteur, and his vision couldn’t be more different from Disney’s. There is no good and evil in Miyazaki’s world, and few heroes and villains. There are no show-stopping ballads. Animals are animals, not wisecracking sidekicks. Children are not idealized: they are resourceful but prickly, cunning but confused. Fear and uncertainty abound. The strangeness remains. In Spirited Away, Sen, the young female protagonist, is shadowed by an eerie, whimpering spirit named No-Face who wears a mask and, craving communion, eats everything in sight. In The Wind Rises, Jiro strides along the wings of a soaring airplane with his dream-mentor, Italian aeronautical engineer Gianni Caproni, and plummets to earth after pulsating black blobs knock him out of the sky.

Over the course of his career, Miyazaki has cited various authors and filmmakers as influences: Antoine de Saint-Exupéry, Akira Kurosawa, Ursula K. Le Guin. But in some ways the artist he most reminds me of is Maurice Sendak. As I wrote in 2009, Sendak knew that the greatest children's stories are about what happens when we become untethered from authority, whether by disobedience, disaster, or disregard, and the twinned feelings of freedom and fear we experience as we grapple with an autonomy we're not quite ready for. They are, in that sense, rehearsals for adulthood.

Like Sendak, Miyazaki is somewhat cranky—a pessimist at odds with modernity. “I want to see the sea rise over Tokyo and the NTV tower become an island,” he told The New Yorker in 2005. “I’d like to see Manhattan underwater. I’d like to see when the human population plummets and there are no more high rises, because nobody’s buying them. I’m excited about that. Money and desire—all that is going to collapse, and wild green grasses are going to take over.” But he also admires the strength of children, and honors it in his work.

To a young fan, Miyazaki’s movies begin, over time, to seem more like memories—like experiences she has had—than like stories she has seen on screen. They help her wrestle with things that are difficult to understand because they themselves are difficult to understand. They help her deal with the terror of being 9 years old because they themselves are, at times, terrifying. Miyazaki, like Sendak, doesn’t treat children like children. He treats them like people. As he once said of Spirited Away, “It's not a story in which the characters grow up, but a story in which they draw on something already inside them, brought out by the particular circumstances. I want my young friends to live like that, and I think they, too, have such a wish.”

Miyazaki will be missed. Today’s animated features can be brilliant, especially Pixar’s. But with their frantic pace, rapid gags, madcap physical comedy, talking animals, crystalline plots, and winking pop-culture references, even the best contemporary examples seem preoccupied, above all else, with keeping children entertained. They steamroll the inevitable digital distractions. They cater to ever shorter attention spans. They provide constant, readymade stimulation.

Yet the greatest children’s stories—the Sendak books, the Miyazaki movies—go deeper. They don’t just create an entertainment. They create a wilderness: an untamed space where kids can wander and roam; where they can get lost and find themselves; where they can be perplexed and surprised; where they can chart their own course; where they can linger on the rattling pebbles at the end of an earthquake.

Miyazaki himself put it best. "I don’t believe adults should impose their vision of the world on children," he said a few years ago. "Children are very much capable of forming their own visions." Without him, those visions will now have a little less room to take shape.