▁Un answer ed , ▁Kim ▁T ae - ky un ▁began ▁to ▁work ▁on ▁his ▁script ▁and ▁finished ▁it ▁after ▁five ▁years . ▁During ▁that ▁time , ▁he ▁frequently ▁interview ed ▁the ▁detect ive ▁who ▁worked ▁on ▁the ▁case ▁for ▁his ▁script ▁material . ▁Princi pal ▁phot ography ▁began ▁on ▁August ▁ 1 4 , ▁ 2 0 1 7 ▁in ▁Bus an , ▁and ▁finished ▁November ▁ 6 , ▁ 2 0 1 7 . ▁ ▁Release ▁ ▁The ▁film ▁was ▁released ▁in ▁South ▁Korea ▁on ▁October ▁ 3 , ▁ 2 0 1 8 , ▁alongside ▁Hollywood ▁films ▁Ven om , ▁Christopher ▁Robin ▁and ▁Sher lock ▁G nom es . ▁On ▁November ▁ 5 , ▁ 2 0 1 8 , ▁it ▁was ▁released ▁in ▁V OD ▁services . ▁ ▁On ▁August ▁ 2 0 , ▁ 2 0 1 8 , ▁the ▁film ▁received ▁a ▁R - rating ▁from ▁the ▁Korea ▁Media ▁R ating ▁Board , ▁where ▁the ▁film ▁is ▁intended ▁for ▁aud ien ces ▁aged ▁ 1 9 ▁and ▁over . ▁Rep lying ▁to ▁media , ▁the ▁film ' s ▁production ▁company ▁stated ▁that ▁the ▁film ▁did ▁not ▁contained ▁' such ▁strong ' ▁restricted ▁content ▁( such ▁as ▁violence ▁and ▁g ore ), ▁and ▁they ▁believed ▁that ▁it ▁is ▁mil der ▁than ▁two ▁other ▁ 2 0 1 8 ▁released ▁films ▁Bel ie ver ▁and ▁The ▁W itch : ▁Part ▁ 1 . ▁The ▁Sub version , ▁which ▁both ▁received ▁age ▁ 1 5 ▁rating . ▁As ▁such ,