SEOUL, Aug. 21 (Yonhap) -- Actors Park Hae-il and Park Seo-jun will star in director Lee Joon-ik's new film, tentatively titled "Firefly."

Production companies Migo Works and Kirin Film said Friday that they have cast Park Hae-il and Park Seo-jun in the film and will begin shooting next month.

"Firefly" follows Jun-gyeong, a detective in 1974 seeking to escape the stigma of guilt by association, as he travels to the fictional village of Hwayong-myeon after a mysterious man named Man-seop.

The film is Lee's first since "The Book of Fish" (2021). The story moves between 1974, under dictatorship, and 1950, when the Korean War broke out, as it traces the truth behind an incident that remained hidden for 24 years, according to the production companies.

Park Hae-il will play Man-seop, a mysterious figure who tells Jun-gyeong that there is "a case that will bring great results" and takes him to Hwayong-myeon, drawing him into the heart of the case.

Park Seo-jun will portray Jun-gyeong, a detective whose career prospects have been blocked by guilt by association.

Choi Dae-hoon, known for the dramas "Kim Bu-jang" (2026) and "When Life Gives You Tangerines" (2025), will play Tae-sik, a deputy director of the Korean Central Intelligence Agency who prides himself on being a patriot.