Ambition can be quite deceiving. But it is not just the ambition a person has himself, but also that of individuals who are close to that person. And the theme here is quite something. Infidelity is wrong (at least morally above all) - but how does that make an impact on a couple? And what lengths should they go for their own goals? It is these questions the movie asks, that are quite riveting and that are really relatable.
I am a bit surprised this has such a low rating and I have a bit of an affection towards Korean movies from the get go, so maybe I am biased. But as mentioned this really does not just go for society as a whole (not only the upper class, though they are the "main" target), but really focuses on the personal level and sacrifices when it comes to the way to the top ... The ending may be something that people will disagree with, but I liked where it went and I liked the realness of the characters too (flaws and all)