How ‘Sleep’ Director’s Mentor, Bong Joon-Ho, Gave Him the Confidence to Pull Off a Wild Blend of ‘Rosemary’s Baby’ and ‘Erin Brockovich’

Jason Yu’s feature debut, “Sleep,” is a supernatural domestic thriller about a South Korean couple named Soo-jin and Hyeon-soo (Jung Yu-mi and Lee Sun-kyun) who are torn apart by his increasingly dark sleepwalking habits. As they welcome a baby into their world, things take a turn for the worse, and she investigates what is really causing her husband’s frightening behavior. Yu cut his teeth as Bong Joon-ho‘s right-hand man during the two-and-a-half-year filming of “Okja,” and considers the director a mentor and inspiration for the project. He also counts Lee, who died in 2023, as a person who deeply influenced him as a filmmaker. Yu spoke with Variety about crafting his horror around a family drama, films that inspired him and the best advice he got from Director Bong.

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Where did the idea for “Sleep” originate from?

I too have some very nasty sleeping habits. Not as nasty as what transpires in the film, but I’m a very loud snorer and have a serious case of sleep apnea, which is forgetting to breathe while you’re sleeping. The loud snoring didn’t bother my wife that much, but whenever I stopped breathing, that’s when my wife would wake up and be frightened. In the morning, she would tell me about these anecdotes, and although I felt immense guilt and I felt sorry that she had to go through that, I think the storyteller in me was fascinated by what happened at night. I imagined what would happen if my sleeping habits were slightly scarier.

Did the script always focus on so many marital and family issues?

It was something that came later. I first approached it in a very pure horror way, and it felt a bit repetitive and gimmicky to me — so much so that it didn’t excite me at all. So I shelved the idea for quite a long time. But when I returned to the story, my situation was slightly different. I was preparing to marry my longtime girlfriend, and my now-wife and I were thinking a lot about marital relationships, lots of meetings with the in-laws, just wondering about parenthood and all that, but mostly marriage and the idea of what it could be. Those personal aspects, unbeknownst to me, seeped into the screenplay.

What were some of the films that inspired “Sleep”?

I was retroactively told by the audience members of various festivals what my influences were after watching the film. They would ask me, almost rhetorically, whether I was influenced by films like “The Shining” and “Rosemary’s Baby,” and it was only then that I connected the very large dots that were in front of me. Just the basic premise of “Sleep” — the pregnant wife, the husband character and their relationship inside the single-location building — was greatly influenced by “Rosemary’s Baby.”

A very unlikely influence is “Erin Brockovich.” Jung asked me, “It doesn’t feel like most people would act like this — they’d probably just flee or separate.” And I told her, “Well, this person isn’t an everyday person.” I think Soo-jin is more like Erin Brockovich, a person who, when obstacles come her way, merely perceives them as obstacles and finds ways to overcome those problems. Soo-jin, like Erin Brockovich, doesn’t yield to the elements that easily. She is very optimistic in her ability to overcome any problem with her husband.

What was your working relationship like with Lee?

Working with Lee was an immense honor because even before “Sleep,” I always regarded him as one of the greatest actors in Korea, if not the world. Interestingly, he had the most experience on set among our cast and crew, so he was like a big brother to us. He didn’t like when we slacked off or showed unprofessionalism, and he would also impart these nuggets of wisdom not even related to acting. Sometimes because of our inexperience we would worry and stress over certain scenes and how to shoot them. He would just walk past us and say, “You know, you can just do this, this and that and it will be good.” He was absolutely correct, so he was almost like a producer in that way. He had so much wisdom to impart. I was very grateful for that.

The central relationship feels real real, not just movie real. Was there a moment during filming where you realized the chemistry was there?

Absolutely. That was my main concern before going into shooting. I suggested to my two actors, “Maybe you guys could go on an ice cream break or have dinners or go for walks in the park just to cultivate this chemistry.” But they cut me off immediately saying it was unnecessary because they already starred in four films where they were romantic interests, and they were great friends in real life, so they already had the chemistry down. Although I had some trepidation and concern, everything melted away on the first day when we had to shoot this very intimate, loving scene between the two and they nailed it on the spot.

What is the best advice you got from Bong Joon-ho about directing?

After I gave him my screenplay and he read it, we met in a cafe. Although I’ve written a screenplay like many ADs, I thought directing would be a pipe dream. I was looking for a job and I kind of was there to beg director Bong to have me for his next project, and what he said was, “Forget about that project. This screenplay is really good. I think you should direct it, and I think you can do a great job in directing it.” That triggered something in me. He gave me that courage, and that’s what I took to heart.

The most technical thing was after I completed the screenplay, he told me to draw all of the storyboards, and that’s exactly what I did. I learned from “Okja” that he drew his storyboards, but I later realized not every director does it. Being under the tutelage of director Bong, I drew the first draft of the storyboards myself, and a lot of people said I was out of my mind because it wasn’t even greenlit at that point. There weren’t even financiers who were interested. But director Bong, after reading the screenplay, just told me, “Now it’s time to draw the storyboards,” and that’s what I did.

What plans do you have for future projects?

I have two projects currently that I’m excited about equally, but I do think I have to pick a lane soon. One is in the horror realm, a similar vein to “Sleep,” but slightly bigger in scale. And the other end is quite the opposite: It is one of my great dreams to direct a romantic comedy one day, and the goal is to have the investors, producers and financiers as enthusiastic as I am about the project.