What makes you want to continue watching any series?
One of the less talked masterpieces (amongst others) of this drama was the beginning narration in the pilot episode; that thing makes you anxious, a trepidation to know more, it makes you interpolate with it.
In addition to already talked "good things" about the drama, the first interaction between Gang-tae and Moon Young could be as stoic as it gets. Well, some may brush it off as FATUOUS, but I disagree.
Dare I say Oh Jung-se's performance as Sang-tae is blummin' good which I feel is underappreciated.
Lastly, the undulations in this drama are ubiquitous every episode and that only gets better with their entangled past which is not very pleasant.