I enjoyed the first handful of episodes and thought I would enjoy the series as I've seen the main actors in other dramas. Instead I found the entire series frustrating with no real character growth or takeaways. The music is great though so the very most I will give it is 2 stars. Potential spoilers below.
The main character Hwa-sin is not a good person, not a good family member, is a terrible friend. He is arrogant (what was with the scene in Thailand where he totally disrespects and annoys a random couple) and cold to Pyo Nari from the very beginning (swap a Quizno sub so you can try a different flavor, what's wrong with that!). He can never make up his mind for the entire series - so frustrating to see him continuously go back and forth. He can't even look after himself BY himself? He has no self-control of his own (continues to miss radiation appointments, get in fights, and drinks alcohol) and can't speak up or tell the truth until it's too late and people have either suffered, wasted their time, or died. And he claims to have moved for Ppal-gang but he did absolutely nothing to look after her. This series really missed the chance for him for stronger dialogue and growth for his character. I should also mention how can you call yourself a good friend when you can't even tell him about your health, and you go after the girl that you set him up with.
He's not the only one at fault here. Pyo Nari was overly annoying in this drama. She couldn't ever leave Hwa Sin alone or tell her boyfriend the truth or pick up his calls. In reality, anyone would easily choose Mr. Ko over Hwa-sin. This series really did him wrong and I feel sorry for him. Sure, Mr. Ko could've stepped up on more occasions (he started so strong with pulling her into him during the thunderstorm) and he didn't understand the concept of spending time alone with his girlfriend, just him and Pyo Nari - he had to always invite Hwa Sin along.
I'll tell you a better story. Mr. Ko ends up with Pyo Na-ri with Hwa Sin as his best man. Hwa Sin realizes he's not a great person and that he only wanted what he can't have. He ends up with his partner anchor. She is the one that truly understands him all along, and her family background also helps him to spread truth such as overcoming discrimination and other important issues... Or the series could have just ended 8 episodes earlier where Pyo Nari chooses neither of the two.