People think it's an interpretable ending, if you really analyze the last 15 minutes or so though, you'll see that its not. They both are alive. If you think either of them are dead, you obviously didn't understand it or didn't pay enough attention. The things they talk about at the cafe would make absolutely no sense if they were dead, not to mention her still being partially blind. Yes there are things like Jin Sung and Hee Sun talking about bringing flowers, but those are just elements the director uses to trick us, because we haven't seen the final scene of the show, as it leaves us with more anticipation for the last ten minutes to know what will happen.