''Castaway on the Moon'' is a 2009 Korean film written and directed by Hae-jun Lee. Kim Seong-Geun is a man with no hope left in the world--he was laid off from his job, his girlfriend dumped him, and he is over $200,000 in debt to a shady loan company. So he decides to kill himself by flinging himself off a bridge into the Han River. However, instead of drowning, he winds up washing up on Bamseom Island in the middle of the river, under a bridge. His cell phone's battery dies before he can call for help, and he can't swim, so he winds up marooned on the island, living a Robinson Crusoe existence right in the middle of Seoul.

Meanwhile, Kim Jung-yeon, a young [[{{Hikikomori}} agoraphobic]] woman, has not left her room in three years. She communicates with her parents only via texts, and interacts with the world only through South Korean social network service Cyworld. She takes pictures of the moon because no one's there, and she lives for the semi-annual air raid drills in which the streets of Seoul are deserted. One day she looks out her window with the lens of her fancy camera, and sees Seong-gun puttering around his island. She is fascinated by him, and a strange relationship begins to form between them.

The movie is currently available subtitled on Netflix instant.
!!This film contains examples of:
* ArmorPiercingQuestion: The innocuous question "WHO ARE YOU?" send Jung-yeon into a panic, as she remembers being caught out on Cyworld for using stock photos to create a fake identity.
* AtomicFBomb: Written on the sand, after Jung-yeon panics and cuts off communication between them.
* BoxAndStickTrap: Seong-geun tries this in an effort to catch the pigeons on the island. He screws it up the first time but later successfully traps dinner.
* BungledSuicide: Jumping off a bridge didn't go as planned, but it serves Seong-geun in giving him his own home and a new life.
* ChekhovsGun: Jung-yeon mentions how much she likes it when Seoul has its semi-annual air raid drill, because all the traffic stops and everything freezes. At the end it seems she'll miss Seong-geun, because he boarded a bus that is pulling away. Then the air raid siren goes off, and the bus stops, allowing her to catch up.
* CompanionCube: The scarecrow and duck paddle boat both serve as as stand in friends and consultants for Kim.
* CompletelyDifferentTitle: The Korean title, 김씨표류기, translates out to ''Mr. Kim's Floating Story''.
* DesertedIsland: The way Seong-geun tries to describe it over the phone, and his home for several months.
* EmpathicEnvironment: Jung-yeon freaks out after Seong-geun asks "WHO ARE YOU?". This is immediately followed by a ferocious thunderstorm that wrecks Seong-geun's little habitat.
* FailureMontage: Seong-geun's first attempts to hunt and catch food on the island. He tries to rig up a spear to catch fish, using a stick and a fork, but spears his own foot. Later he gets much better at it.
* GoodSmokingEvilSmoking: The cigarette smoked by Seong-Geun's ex-girlfriend in the flashback adds to her character's callous nature, while Seong-Geun later enjoys one himself without the same connotations.
* GratuitousEnglish: Seong-Geun writes "HELP" on the sand in English, maybe because that's quicker to write than "도와주세요". Thereafter, all communication between Seong-geun and Jung-yeon is in English.
* HoldingHands: The movie ends before they go any farther than that.
* InnerMonologue: The majority of Seong-geun and Jung-yeon's thoughts are conveyed this way
* LoveBeforeFirstSight: A relationship is built on messages and telescopic peeping, before they ever meet.
* MessageInABottle: A variation on the trope. Jung-yeon communicates with Seong-geun by flinging messages in bottles off the bridge, down to the island.
* RightUnderTheirNoses: Seong-geun's "desert island" is in the middle of the city and is right under the bridge over the Han River.
* {{Robinsonade}}: Seong-geun constructs a shelter out of a derelict duck-shaped paddle boat, catches fish and birds, and even gets a little farm going--until the storm wrecks everything.
* ShutIn: Jung-yeon communicates via text. When a noodle delivery guy arrives, she slips the money under the door.
* UnkemptBeauty: Both the leads. One is grimy and unshaven on a desert island, and the other is a shut-in who's not that careful about personal hygeine.
* TheUnreveal: Jung-yeon, otherwise quite lovely, has a scar or disfigurement of some sort on her forehead above her right eye. It's never revealed how she got it, or whether the scar is the reason she's a shut-in.
* VehicleVanish: This happens when Seong-geun jumps off the bridge.
* VertigoEffect: Used when Jung-yeon leaves the apartment for the first time in three years, to send a message to Seong-geun.