I swear, this drama has more makeouts than every other kdrama I've ever seen put together. But shallowness aside, I think it has interesting things to say about relationships - LJW and JYM are sexually compatible and are also very close friends, plus, she is falling for him again and reading between the lines, so is he, so you'd think they would be the perfect couple but that is not the case - she is impatient and very hot-tempered (pretty clearly, every breakup was initiated by her in a fit of temper), plus awful about reading emotional subtleties and he is emotionally shut-down and abysmal about either articulating his feelings or letting her in to see anything vulnerable. Unless they work it out, any attempt to become a true couple again is doomed. It's not that a person with either of their tendencies cannot be in a happy and successful relationship. It's that it would be hard for people with those tendencies to be in a happy and successful relationship with each other. They either need to change or affirmatively accept that this is the way the other person is and work with it, and they haven't so far.
( Caps - mainly of makeouts and sexy sexy Lee Jin Wook )