It's the story of Seo Jung Hoo who is a special kind of night courier, known only as "Healer" by his clients. His latest job leads him to a second-rate tabloid writer, Chae Young Shin, and the successful reporter, Kim Moon Ho. He begins to uncover the mystery of his own shared past with the two reporters, thus putting them all in danger.

This series is a lot praised, and I understand why in the sense that it brings together all the elements of the typical K-Drama. There is comedy, romance, action and suspense, so it is a mix that brings together a lot of people.
And even if we have emotional scenes, and the antagonists always do what the antagonists do, basically bad things, I must say that the drama is really light-hearted and very much cheesy.

Now, I don't mind the fact that it is a series that has been shot in this direction, precisely with the desire to give a light-hearted series for everyone and that also, it is a series that dates from 2014.
I believe that for its genre, and people who love the combination of all these, this kind of series is really good.

My perspective is influenced by the fact that when I look at an action thriller, I expect better, darker and raw, I expect realism. And this is entirely personal, that does not influence the fact that this series is good, but just not my style. "Vagabond" is the same kind of series in the spirit, but to me "Vagabond" did so much better while they had the same elements of romance, comedy and mystery.
This series rather approaches the subject with sometimes incredible scenes, endearing or slightly annoying characters who lack realism, where Seo Jung Hoo, the male lead would have almost supernatural skills at this stage.
I am not a fan of romance, but some series manage to convince me, here unfortunately it was not the case. Not that the two actors were not good, I just didn't felt it.

I would also like to point out the songs and OSTs. I think it's really the only thing that objectively lacks this series. They had a truly light/happy sounding song/instrumental playing in the background while the main lead fought or had intense scenes. It really spoiled the impact of it.
And then I'm not even talking about this English song, which started playing as soon as the two actors (Chae Yeong Shin and Seo Jung Hoo) thought of each other, or had flashbacks, or some random moments. The "Promise me this is forever" really did get on my nerves, it was so cheesy. Also, admittingly I skipped several scenes, specially toward the end, to me this series could have been done with less episodes.

As for the acting. Park Min Young, who performs Chae Yeong Shin was the best for me. Generally, especially in this kind of drama, I prefer male lead, but here I must say that she was the highlight. She was strong and sometimes vulnerable, relatable, funny and kind.
Yoo Ji Tae, played Kim Moon Ho, and this actor that I have seen in several series has still failed to convince me. His acting is barely decent, the only things he shows are to smug face or angry tears. His roles are different but in the end, I always have the impression of seeing the same character in each of these series.
Ji Chang Wook, played Seo Jung Hoo. It is very rare that a male lead does not win first place in my top, and I would not say that it is because of bad acting because it is false, he showed several layers, but I cannot help but being disappointed because I was waiting for more. I'm going to watch others of his series, and I hope that I will find this missing thing to his acting there, but overall he did a good job.

If I had to summarize this series, I recommend it for people who love romances, comedy, action, a very interesting storyline with mysteries to discover. The acting is decent and overall, it's good - nothing more.
On the other hand, for people like me who do not like romances, or series supposedly thrillers but who in reality are more in the category "mystery and action", because it was not a thriller let's be honest, I do not recommend.

I saw the series to see it until the end because I wanted to know how it will end but honestly, if I would have known, I would not have watched it.