The Drug King is set in Busan, South Korea in the 1970s. It tells the story of Lee Tousen, played by Song Kang-ho, who rose from a smuggler with no moral integrity to a legendary drug lord. The prototype of the story is a drug lord who started out as a smuggler in the 1970s and later rose to prominence in the drug manufacturing and trafficking industry. The director said that although Lee Tousen is a fictional character, he used a real drug lord as the prototype and completed the script after several years of data investigation.