Too contrived (Spoilers)
I thought the idea of playing off of the twin brothers would make this a very interesting movie. In theory, it was interesting; in reality, for me, it did not work at all. The idea that each one at different times was in a coma just seemed way too contrived to me. (Even the announcement over the intercom in the hospital describing the musical piece about a woman falling in love with her husband's brother was just plain silly.)
It's also implausible that Jin-Woo could have hidden his limp when he was pretending to be his brother when Yeon came to see him and ended up having sex with him (Jin-Woo). (And SHE'S angry at her husband after she's screwing who she thinks is her brother-in-law? Please. And who is SHE to judge her mother or anyone else for that matter? No sympathy/empathy whatsoever for that ho.)
I also felt that the cutting of this film as well as some of the acting was mediocre. Less than halfway through the movie I honestly didn't care which brother was which, or how things turned out. The brothers were deceitful; Yeon was deceitful. And I'm getting really tired of films about cheating spouses that fail to evoke any empathy for the main character(s).
And the ending was just flat out ridiculous. Clearly, the writer(s) and director were at a loss how to end the film, and decided on a cheap "twist" to tie everything together. But as often happens in those instance, rather than tying everything together, it causes everything to fall apart/unravel.
"Love isn't what you say or how you feel, it's what you DO". (The Last Kiss)