Despite the title, Mr. Sunshine is no romantic fairy tale. Handsome Captain Eugene Choi returns to the land of his birth after 30 years in the USA where he carved a brilliant career in the military, only to find that nothing has changed for the better and the kingdom is now threatened by the increasing presence of the Japanese army.
Joseon's King/Emperor, lacking the support of his ministers and betrayed by many, does not want to create a confrontation with a superior military force fearing it would plunge the country into a bloodbath, so he gives in too often and finally loses the throne. Joseon-Korea ended up under Japanese occupation for 36 years until the end of WW2.
Eugene falls in love with Ae-Shin, a noblewoman fighting for her country, and protects her at the risk of his life and career. Lee Byung-hun makes an excellent captain, his calm demeanor and composure thinly veiling the anguish of his childhood and his now all consuming love for Ae-shin.