It will be their second project together after last year's drama "Little Forest".
Set in the present day, the two-part film will tell the story of aliens living in Korea. It is already generating a lot of buzz, as it is Choi's first film in some five years since "Assassination" in 2015, which drew over 10 million viewers.
Kim is currently shooting another big-budget sci-fi film, tentatively titled "Victory".
Ryu is taking some time off after the release of his latest war film, "The Battle: Roar to Victory", earlier this month.
Shooting for the new film will begin next year.
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