I think this story is more than the obvious infidelity. It is about the need of give and receive love, and about choices. Both, are in dull, cold and passionless relationships. Appart the mental and behavior issues of their relatives are a terrible burden for them. This accidental encounter is like a moment to vent all the pain and even the love they want to feel, which they don't receive from their partners. At the end, choices must be made.
As a production, is excellent! The aesthetics of the scenes are wonderful. The bed scene was perfect, beautiful, no words needed. They communicate to each other and to the audience clear and loud, even in that passional silence. The combination of the actors was definitely great! Again Gong Yoo release all his grace, elegance, boldness and good taste. Do Yeon also...superb! Nobody better for that role. She is experienced and communicates great with soft gestures. I loved this movie. I don't know why I didn't see before.
