I tried to write a review without spoilers but i am sorry this still does contain some minor spoilers.
- !!Disclaimer!!: This is just my opinion about this drama. I don't think this is the Truth of the Truths of this world. I won't recommend this drama to some of my friends, but I will recommend it to some others. So if you want to try this drama and start to hesitate because of this review, please don't :) you can just start it, try several episodes and then decide for yourself! Thank you for reading! -

Doctor john explores the concept of euthanasia, pain, rare diseases, CIPA patients etc. etc.

Well I saw many good reviews so I'll just take the unpopular road this time, with telling the bad things this drama had. very sorry to people who liked this and to people who worked hard making this drama but this was very meaningless and unrealistic story.... I gave rating 4 only for the people who worked on it.

What I liked:
-sister and fellows romance
-kitten
-mom

What I didn't like:
-story (lol)
-characters(lol)
-they mixed too many concepts
-something failed here very badly....
-one-sided answer to a controversial problem.
-main couple's romance
-male lead's occupation
-just everything lol

longer review:

Music was ok, so I just put a random number there. Acting was ok, as they act out the written characters and are not characters themselves. The story/plot.... well this is where the real issues start.
First of all this drama started with prison and showing Doctor Yo Han as some brutal mysterious guy stitching himself. Plus the main female lead Kang Shi Yeong who was constantly crying for any reason. Well at first we don't know the reasons so it's ok. And when we learn her reasons we start to understand her. But she keeps crying even for reason unrelated to her problem, for any little thing. Anyway... after that the whole story goes to hospital. The prison part was extremely unnecessary. It was just a useless way to keep viewers, because 1) it's prison and that itself is usually intriguing, 2) Yo Han was shown very mysterious, which was captivating. BUT It didn't help the plot at all. They could have just stated about prison and that's all.
After that we see them working in hospital. And the problem of euthanasia rises more. We see two people who are fiercely fighting against it, and also the lead who doesn't say anything. So here i thought oh wow this explores that problem it's great! However the drama suddenly starts exploring rare diseases. and you get one rare illness after another and the doctors are like investigators trying to find the culprit. Why, oh why should the anesthesiology department be the only place where people can do diagnosis. Yo Han could have just been a person who gives diagnosis, like doctor House and it would have been awesome. But somehow anesthesiologists do that job. Then they start talking about pain. How people feel pain, what is pain, for what, and about people who don't feel pain at all. Cha Yo Han says many nice quotes. But wait... this is already like 3 different dramas. O_O and all this time Kang Shi Young was following Yo Han a bit like a stalker and crying all around about him not telling her this or that, not being careful etc etc. I felt no chemistry between them, to be honest. It felt very forced and one-sided.
during all this time they were showing some secret group which was somehow related to that problem of euthanasia.
In the middle of the drama the two people who were fighting against euthanasia turned out to be simply crazy. while the drama was showing them so full of justice at first.
Might think this just explores that problem more and more, but in the end it gives a clear answer: "we are against euthanasia, and it is murder". they don't say it like this but this is what is implied very strongly during the last 4 episodes.
The secret organization only truly appears during one episode and then no one even thinks of searching them more.
takes shift to the forced romance and ends, leaving in darkness so many doors they opened randomly but never really showed us the rooms. Him willing to be a doctor like that even while dying also didn't make sense, he totally could be someone who makes diagnosis. that would suit him much better and that was what would needed from that person. This was very meaningless and unrealistic story. Maybe the writer wanted to explore many problems and wasn't sure she will be able to do it in other dramas and decided to use everything here. lol Well this became a grey mixture not even captivating enough.
The characters were also written poorly. Cha Yo Han as I already said is perfect at making diagnosis but somehow he is anesthesiologist, and even performing surgeries sometimes(!!!) I mean not just going there checking the patients sleep and all, but really doing stuff.... lol also treating many patients. their department looked more like the emergency center of rare diseases. In the middle of the drama he starts to act like a girl lol with female lead being all protective and him accepting everything and falling for it. lol Kang Shi Young was a character that cried a lot, got in the way a lot. They tried to show her as a strong person but she wasn't. Her big problem became not so big of a problem later just because she met him and her head was full of him. All the stuff she said was not so nice. I mean i would have gotten angry if someone talked with me like that. told that kind of stuff and cried all the time. The two other resident guys were just funny comedians, not even knowing english... just how in the world did they become doctors. The only nice characters were Kang Shi Young's mom. sister and the other doctor that plays Mugwang (cursed guy) in Arthdal chronicles. Their romance with kitten was nice.
P.S. I watched this with my mom and she was even disappointingly asking how the actors could choose such a drama and how directors could agree to shoot it and no one told the plot as big holes in it.