General · EdgepediaOctober 3, 20266 min read

Sleep (잠) (2023 film)

Sleep (잠) is a 2023 South Korean psychological horror film directed by Jason Yu (유재선) in his feature debut, starring Jung Yu-mi as the pregnant Soo-jin and Lee Sun-kyun as her husband Hyun-su, an actor whose sleepwalking becomes increasingly grotesque and threatening.¹^•² It premiered in the Critics' Week section of the 2023 Cannes Film Festival and was released in South Korea on September 6, 2023 by Lotte Entertainment.³^•¹

Key fact	Detail
Director and writer	Jason Yu (유재선), a former assistant director to Bong Joon-ho; his first feature⁴
Cast	Jung Yu-mi (Soo-jin), Lee Sun-kyun (Hyun-su), Kim Keum-soon (the shaman)²^•⁵
Release	September 6, 2023 (South Korea, Lotte Entertainment); September 27, 2024 (United States, Magnolia Pictures)¹^•⁶
Runtime and rating	94 minutes; rated 15 in South Korea¹
Festivals	Cannes Critics' Week (2023) and Toronto (2023)³^•⁷
Box office	1,470,553 admissions in South Korea; $10,259,934 there and $11,063,144 worldwide¹^•⁶
Critical scores	95% on the Rotten Tomatoes Tomatometer from 84 reviews; 6.6 on IMDb²^•⁵

Spoilers

Premise and plot

The film follows newlyweds Hyun-su and Soo-jin, whose domestic life is disrupted when Hyun-su begins speaking in his sleep, ominously saying "Someone's inside." From that night on, whenever he falls asleep he transforms into someone else, with no recollection of what happened the night before.² Soo-jin, an office worker in the last month of her pregnancy, becomes overwhelmed with anxiety that he may hurt himself or their family and can barely sleep; when a sleep clinic fails to help and his sleepwalking intensifies, the couple turns to a shaman.³^•²

A Korean-language scholarly analysis describes the film's structure in three parts: the first shows the newlyweds' happy daily life breaking down as Hyun-su's somnambulism begins; the second, opening with Soo-jin's childbirth, brings sharpened tension into the home as her neurotic protectiveness of the child grows; the third brings her frenzy to a peak and turns the apartment into a stage for an exorcism rite.⁸ The same analysis notes that the film makes the vulnerability of the body a source of horror, since Soo-jin is heavily pregnant and Hyun-su is an actor who performs with his body, and that Soo-jin's driving motive is the ideology of the normal family.⁸

Director and production

Jason Yu worked as an assistant director to Bong Joon-ho, the Oscar-winning director of Parasite, before making Sleep his feature directing debut; the film was produced by Lewis Pictures, the company behind Okja.⁴ Yu said he chose the title because the film depicts how to unravel a frightening mystery and how to make one's way through a nightmare-like situation.⁹ Bong Joon-ho praised the film's unpredictable drama and called it "the most unique horror film" he had seen in the last decade.⁴

The production design centers on the couple's apartment. BFI Southbank's program notes describe the bedroom where the couple appears to sleep and the house embodying their everyday life as more than physical spaces, representing the intimate worlds that give the film its distinctive horror, with camerawork used to convey the psychological states of both characters.¹⁰

Release and festivals

Sleep was screened in the Critics' Week section of the 2023 Cannes Film Festival, which focuses on first and second films by emerging directors, and also played at the 2023 Toronto International Film Festival.³^•⁷ It opened in South Korea on September 6, 2023 on 1,231 screens.¹ International releases followed, including France on February 21, 2024, the United Kingdom on July 12, 2024, and a limited United States release on September 27, 2024 through Magnolia Pictures.⁶ The film later became available on streaming services including Hulu and Disney+ in the United States.²

Reception

The film earned a 95% Tomatometer score on Rotten Tomatoes from 84 reviews, with the site's critics consensus calling it "elegantly executed" and saying it "builds prosperously upon a familiar premise and delivers rousing chills"; the audience Popcornmeter score was 71%.² Reviewers highlighted the tonal mixture. Virginie Sélavy, writing in Sight and Sound, described a film that alternates light-hearted domestic comedy with unsettling nocturnal horror, contrasting the charming husband with his sinister night-time alter ego.¹¹ Peter Bradshaw of The Guardian called it an elegant, intimate chiller from a former assistant to Bong Joon-ho, with hints of The Exorcist and Sleeping with the Enemy.¹² Simon Abrams at RogerEbert.com judged that the film avoids becoming a lame horror comedy and instead works as a fine-tuned marital drama and slow-burning ghost story, aided by the chemistry between Jung Yu-mi and Lee Sun-kyun in one of the actor's final roles.¹³

Awards. Sleep won the Grand Prix at the Festival International du Film Fantastique de Gérardmer, the French horror festival that has honored the best horror, mystery, and science fiction films since 1994.¹ Yu Jae-sun received a screenplay award for the film,¹⁴ and Jung Yu-mi won Best Actress at the 2023 Korean Film Producers Association Awards.¹⁵ The film was also selected in the film section of Beksul Choice 10, where programmer Lee Hwa-jung praised its heroine Soo-jin as a character who, frightened but unyielding, breaks the horror genre's stereotype of passive women.¹⁶

Themes and place in Korean horror

The film departs from the convention of ghosts or spirits as the source of fear; its premise is instead the eerie transformation of the person who sleeps beside you every night, behaving as if they have become someone else.¹⁰ Yonhap's review described it as a fusion of horror, romance, and mystery thriller inspired by Korean contemporary culture of apartment living and shamanism, the latter a practice of healing rituals focused on spiritual causes of sickness.³ The BFI lists Sleep among ten great South Korean horror films, placing it in the domestic-strain tradition of Korean horror begun by Kim Ki-young's The Housemaid (1960), and notes that it is shrewdly ambiguous about the causes of the husband's disorder while dissecting marriage with precision.¹⁷ Critics have also read the film through the fears of new parenthood and sleep deprivation, with both spouses cast in turn as dangers to the family.¹¹^•¹⁸

Lee Sun-kyun, known internationally for Parasite, died in December 2023, making Sleep one of his final roles.¹³^•¹⁹

References

Initially written Oct 3, 2026 · Reviewed: Oct 3, 2026; Oct 25, 2026 · Edited: Oct 15, 2026; Oct 25, 2026; Nov 1, 2026