In a 2024 interview with The Moveable Fest, Jason Yu spoke about how he came to direct the film, his first: "Before directing 'Sleep,' I was an assistant director for various Korean films, and one of them was Okja (2017) by director Bong Joon Ho. Usually what assistant directors do in Korea, unlike the United States where it's a lifelong profession, is that it's a temporary profession for aspiring directors who learn the craft and between projects, they write their screenplays in the hopes that they get made. Then once you complete your screenplay, the first person you show it to is your mentor, the director you AD'ed for. And in my case, that was director Bong Joon-ho.
So I remember being in between jobs, and being unemployed and begging director Bong to let me be an assistant director for his next project and we scheduled like a coffee meeting. And while we had this coffee meeting, while I had him there, I gave him my screenplay [for 'Sleep'] for him to give me notes on. And after reading it, he said, 'Jason, I think you should forget about my next project. You should direct this because this is a great story that you've written and you'd be really great at that.' That's when this pipe dream of becoming a director [seemed] actually within arm's reach and although I was an AD and an aspiring director, it never really felt tangible. It was just something in the far future that might happen and might not. But when he said that, I realized this is a very realistic thing that I can do. He really gave me that courage and confidence for me to really pursue directing this project, which was a very memorable moment for me."