In director Jason Yu’s “Sleep,” newlywed Soo-jin (Jung Yu-mi) finds out her husband Hyun-soo (Lee Sun-kyun) suffers from a very bad sleeping habit.

Soo-jin’s loving husband becomes a completely different person at night. On top of sleepwalking, he scratches his face until it bleeds or opens the refrigerator and munches on raw meat, fish and uncooked eggs. To protect their newborn baby, Soo-jin is willing to do even crazier things to confront her fear.

The 94-minute film is seemingly a mystery thriller revolving around a husband with somnambulism and his wife who believes he may be possessed by a demon. What’s unique about this film is that it’s a story of newlyweds who keep reminding themselves that “there is nothing we cannot do when we’re together” – a family slogan written on a wooden board hanging in a living room wall.

The film, divided into three chapters, rapidly unfolds the story of Soo-jin and Hyun-soo, with each chapter showing a starkly different mood and mental state of the characters. While the first chapter surprises the audience with Hyun-soo’s strange, even grotesque sleeping habit and hints at a crisis that the couple is about to face, the second chapter leaves the audience wondering who is crazier or scarier – Soo-jin or Hyun-soo.

Although no ghost or cold-blooded serial killer appear, the tight running time never lets the audience put down its guard. The idea that a loved one who who acts loving during the day time, but can become dangerous at night create a sense of anxiety. Adding to this tension is the portrayal of home as the most likely place where atrocious incidents occur.

As the film proceeds, it becomes not just about overcoming fear, but real bonding between a married couple. Soo-jin and Hyun-soo do not leave one another despite a series of unfortunate events. The film’s director Yu said part of his own real life story is embedded in the plot.

“When I was writing the scenario, I was also preparing for my wedding. That influenced me not to portray this couple too darkly, but rather focus on how the couple tries to resolve the problem together as a family,” Yu said during an interview with The Korea Herald in Seoul on Aug. 23.

The couple’s tight grip on each other is in contrast to the people around them, such as Soo-jin’s mother, who tries to persuade Soo-jin to simply get a divorce. For a long time, the mother had disliked Hyun-soo, an unknown actor who makes little income. Soo-jin’s neighbor casually tells her that if something is difficult in her life, she should simply walk away from it.

While “Sleep” depicts some endearing aspects of this struggling couple, the film also has elements of a black comedy. Actor Jung Yu-mi playing a character driven to madness proves why Jung was director Yu’s first choice. Lee Sun-kyun said in a recent interview that it was Yu who reignited in him a fresh passion for his craft with the challenging role.

Having worked with the Oscar-winning director Bong Joon-ho in “Okja” (2017), director Yu seems to have put everything he learned from Bong in this debut feature film. The realistic and detailed portrayal of the characters, the simple and succinct plot and the efficient storyboard-based directing were what led to Bong’s praise of “Sleep” as the most unique thriller flick he has seen in a decade.

“Sleep” hits local theaters on Sept. 6.