As has been pointed out by other reviewers, this story is a new spin on "The Prince and the Pauper." It actually reminded me, however, of the American movie "Dave," in that the protagonist is a naive pawn whose empathy allows him to rise to the occasion, including finding love in the chaos.
Byung-hun Lee is simply an amazing actor. Having seen his "dark" side in movies like "A Bittersweet Life" and "I Saw the Devil," I was very pleased to see he could handle the role of Ha-Seon with such a light touch. It was a joy to see him effortlessly shift from hilarious toilet humor to inspiring leader. I was particularly struck with the scenes where he interacted with commoners, in which I really felt the empathy Ha-Seon felt for them.
This is the first of director Chang-min Choo's movies I've seen, and I was impressed at how he was able to seamlessly balance the light and serious scenes in the movies. To often, one or the other seems forced, but here Choo creates a character who grows and changes, but still remains, at heart, the same, good person he was at the beginning -- the kind of person who, by the end of the story, could be happy and believable as a king or a pauper. I think Choo also gave the movie a more intimate feel by focusing on one-on-one conversations and limiting the normal "cast of thousands" you often see in period pieces about kings.
Overall, the acting was top notch -- particularly from Hyo-ju Han as the Queen and Hyo-ju Han as Minister Do -- and the costumes and set design were beautiful.
Masquerade is an engaging and charming period piece with humor, action, and romance.