Jo In-sung
Jo In-sung was on board from the beginning of the project, and turned down other acting roles to make "A Frozen Flower" his last work before enlisting for military service. He chose to appear in the film without knowing the exact details, having faith in the director following their earlier collaboration in 2005 on "A Dirty Carnival". Jo began training for the role in August 2007, learning martial arts, fencing, horse riding and geomungo. The casting of Joo Jin-mo as the king was announced in December 2007.