A man leaps from a bridge over the Han River, the pulsating epicenter of a Seoul that never stops. This is no tragic gesture à la Albert Camus, nor a nihilistic scream à la Dostoevsky. It is, in its clumsy and pathetic execution, the last, flaccid act of surrender by a salaryman crushed by debt, a mass-produced ghost of South Korea’s hyper-competitive capitalism. But fate, or perhaps just the current, has a cosmic irony in store for him. Instead of oblivion, Kim Seong-geun (a magnificent Jung Jae-young) finds himself shipwrecked on Bamseom, an uninhabited island and nature preserve in the middle of the river—a black hole of wilderness perfectly visible from the skyscrapers that vomited him out. This is the opening of "Castaway on the Moon" (original title Kimssi pyoryugi, literally “Mr. Kim’s Drifting”), and in this premise lies the full subversive genius of Lee Hae-jun: a radical deconstruction of the castaway topos, a Robinson Crusoe for the Lehman Brothers era, where the desert island is not some exotic elsewhere, but a surreal crack in the metropolitan asphalt.

Cinema has accustomed us to the castaway as the archetype of man struggling against a malevolent Mother Nature, a man who contrives to dominate his environment and impose his own civilization (Defoe) or, conversely, regresses to a primordial state (Golding). Mr. Kim, however, fights against nothing. Civilization is right there, within view, a mirage of glass and steel that ignores him with monumental indifference. His cries for help are lost in the hum of traffic; his desperate signals are mistaken for the eccentricities of a vagrant. His island is not a physical prison, but an existential limbo. He is excluded, but he is not alone. It’s the perfect metaphor for urban alienation: to be surrounded by millions and yet feel invisible. His initial struggle for survival is a farce. He tries to call for help on a dead cell phone, scrounges for edible food among the refuse washed ashore by the current. He is a modern man, stripped of his gadgets and social superstructures, reduced to an almost comical incompetence.

But it is precisely in this emptying-out that his rebirth begins. Lee Hae-jun orchestrates this transformation with the grace of a Jacques Tati comedy and the depth of a Zen parable. Mr. Kim stops trying to “return” and starts to simply “be.” He learns to fish, to farm, to build a shelter. But his true, titanic project, his Holy Grail, becomes the preparation of a bowl of jjajangmyeon, noodles in black bean sauce. This obsession is no mere gastronomic whim. It is an almost divine act of creation, an attempt to recreate from scratch a symbol of comfort and normalcy, a flavor that is the quintessence of his former life. His quest for improvised ingredients—growing corn to make flour, gathering bird eggs—becomes an epic in miniature, a Homeric poem of do-it-yourself that is at once hilarious and moving. He is rebuilding a world, not to imitate the one he lost, but to distill it to its purest, most desirable essence. It is Thoreau’s Walden reimagined by a desperate office clerk, who finds his transcendence not in the contemplation of nature, but in the taste of a bowl of noodles.

If the first half of the film is a brilliant rewriting of the castaway myth, the second introduces another castaway, one whose island is even more impenetrable: a single room. Kim Jung-yeon (an extraordinary Jung Ryeo-won) is a hikikomori, a voluntary recluse who has not left her bedroom in three years. Her window on the world is a computer screen, her only human contact the updating of her avatar on Cyworld, the then-ubiquitous Korean social network. She lives in a curated, artificial digital universe, a cocoon of solipsism where every interaction is mediated, safe, and fundamentally false. Her routine is an obsessive liturgy: she wakes when the world sleeps, photographs the moon (her only, constant companion), and manages her virtual identity. She is the other side of the same coin of alienation: if Mr. Kim was physically expelled from society, Ms. Kim has psychologically expelled herself.

Their meeting is a miracle of pure cinematic screenwriting, an idea that would be the envy of Charlie Kaufman. During her annual urban landscape photography session—a ritual to feel part of the world without touching it—the young woman zooms in with her telephoto lens on Bamseom island and discovers “him.” She sees the word “HELP” written in the sand, which the man, in a fit of newfound serenity, soon changes to “HELLO.” To her, this man is not a castaway to be saved, but an alien, a celestial phenomenon, a fascinating anomaly that has broken into her sealed reality. She begins to observe him, to document his life. Her gaze, initially that of an almost scientific voyeur, slowly becomes tinged with empathy, with participation. He becomes her favorite show, her own private soap opera. It is a version of Hitchcock’s Rear Window stripped of all suspense and reloaded with a romantic melancholy. There is no crime to solve, only a soul to discover.

The communication that develops between these two hermits is one of the most poetic and anti-modern ever seen in cinema. He writes messages to her in the sand; she replies by throwing him a message in a bottle, like an epistle sent across time and space. Later, she will finally leave her house (a heroic undertaking, filmed with the tension of a space mission) to secretly deliver him a package of instant noodles, her “jjajangmyeon.” Theirs is a slow, arduous, asynchronous communication. It is the exact antithesis of the instant message, the “like,” the notification. Every message requires effort, intention, faith. It is a connection built on the desire to be seen, not on the demand to be heard. In an era that was about to be devoured by the hyper-connectivity of social media, "Castaway on the Moon" is a moving and prophetic hymn to the beauty of distance and the sanctity of waiting.

The film is a subtle yet sharp critique of the South Korean society of its time, a nation that, after its economic miracle, was coming to terms with its collateral victims. Mr. Kim’s debt and Ms. Kim’s social anxiety are not individual eccentricities, but symptoms of a collective pathology. And yet, Lee Hae-jun never points a finger. There is no anger in his film, but a deep, tender compassion. He prefers parable to denunciation, poetry to polemic. His direction is precise, elegant, and full of visual inventions that transform the banal into the magical: the reflection of the city on the water that looks like an inverted starry sky, the girl’s room as a lunar diorama, the parallel editing of their solitary lives creating a silent dialogue.

When the inevitable “rescue” arrives, in the form of an island cleanup crew during an anti-terrorism drill, it is not a liberation, but a violation. The outside world bursts into their private Eden, destroying Mr. Kim’s hut, erasing his three months of authentic life, and re-imposing the “failure” identity from which he had fled. It is here that the film makes its final, desperate romantic leap. The girl, seeing her “alien” being dragged away, finds a strength she never knew she possessed. She runs. She leaves her room, descends the stairs, and hurls herself into the streets of Seoul, braving the sun, the crowds, her own fears. She runs for the bus that is taking him away, in a breathtaking sequence that is pure cinematic heart-pounding. We do not know if they will reach each other, if their fairytale love can survive contact with brutal reality. But that is not the point. The film closes on a note of radical hope: true salvation is not being found by the world, but finding a reason to run toward someone. "Castaway on the Moon" is an existential romantic comedy, a fable about isolation in the age of communication, a small, quiet work that contains the vastness of a universe. It is a gentle masterpiece, a message in a bottle cast into the great sea of contemporary cinema, waiting for a lonely soul to find it and feel, for a moment, a little less alone.