"Diary of a Night Watchman" tells the story of the "Night Watchmen", a special patrol team responsible for catching ghosts during the Joseon Dynasty. Jung Yunho will play a pure male character who is loved by many women for his handsome looks, but deep in his heart he only loves one person. Jung Il-woo, who was confirmed to star in "Diary of a Night Watchman" before Jung Yunho, will play a Joseon prince who becomes a night watchman because of his special ability to see ghosts.