Actor So Ji-sub said director Yoon Jong-seok's handwritten letter was part of the reason why he was so drawn to “Confession,” a mystery thriller that tells the story of a man suspected of murder. “When Yoon suggested that we work together on this project, he gave me a handwritten letter that included details about the character and why he wanted to work with me. I was touched by his kind words. And of course, the gripping story filled with twists was another reason I chose to take part in it,” So said during a press conference for the film in Seoul, Tuesday.