I have to start this off by saying this show's prerequisite for success is the dynamic between the trope of Badass and Child (though Myeong-jun's personality is kinda like Jackie Chan.) and gotta say IT WORKED. I absolutely loved their dynamic once I got immersed past Ep 1. The story often uses commonly used but still effective plot points: kid with cancer and tsundere character. Hey, nothing pulls on the heartstrings more than a parent trying his best to save his kid.
IT IS a bit frustrating at times I have to admit especially mid season 1. Although the finale made up for it in the end, it is one of the best finales I have watched for a while, made me tear up.
All in all, the premise is not that unique, we have seen in all forms of media the trope of protector and the protectee (Walking Dead, Last of Us) but the decision to make Myeong-jun whacky and hilarious instead of the stoic, unemotional protector is excellent. Ro-hee as well, though her sometimes monotone delivery of dialogues is kinda "eh". But the actress could act when the script calls for it.
Great acting, decent story. They shouldnt make a Season 2 if they are thinking about it. It just ties up nicely even with the twist at the end.