According to Hwang Jung-min, each country sets a different tone for the character: when the movie is initially set in Japan, it features an overall gray tone. It becomes darker when his character In-nam is in Korea, but suddenly turns red when he arrives in Thailand to carry out his last mission. The red color best represents his true personality.
Hwang Jung-min said the most challenging scene was the one filmed at a shabby hotel in Thailand. Its narrow hallway made staging action scenes very difficult. The warm weather made the work much more exhausting. But they exchanged ideas with the martial arts director and cinematographer and rehearsed the actions several times to prevent injury.
About 80 percent of the film was shot in Thailand.
Just like the audience, Hwang Jung-min also felt great excitement when he faced Lee Jung-jae as Ray in the film. They talked a lot before the action scenes.
Lee Jung-jae found the action sequences in Thailand more spectacular than he expected. He had to familiarize himself with a seamless sequence of moves and practice with the martial arts team for weeks.