I'll be honest, I put this drama off for a long time because I didn't think it would be that good. I heard a lot of good reviews but thought they were exaggerating... they weren't :)
The story is amazing. The little animations are super cute and nicely done, the little stories Ko Moon Young write are also good an interesting. The actual drama's storyline is unique and I haven't watched a kdrama with a similar one before. The storyline about mental health included all different types showing the good and the bad and it was really well done. The fact that the main characters themselves also had their own issues which you discover as the show goes on adds to the idea that everyone has their own problems but you can get through it, whether it be physical or mental. the only issue I had with the storyline was everyone telling Moon Gang Tae to look after his brother as though that's not what he's been doing his whole life, and thus had no life of his own. I understood, however, as many people didn't know his backstory as we, the viewers, did (his mother saying she had him to look after his brother and being killed early in their life). I actually got emotional in a lot of the episodes because the story of different patients got to me as did how relatable the problems some of the characters went through (though not on such a dramatic scale).
Kim Soo Hyun and Seo Ye Ji's acting was incredible, I hadn't watched a drama with either of these factors so I wasn't sure how they would be but they were brilliant. They portrayed their character so well as did the supporting cast. those portraying characters with mental illnesses did exceptionally well, especially Oh Jung Se who played the brother, Moon Sang Tae, who had autism. Just to make this drama even more amazing, the soundtrack was incredibly fitting. I have saved a lot of the songs from this drama to my playlist because they're so good.
Overall this drama made me laugh and cry and I would 100% recommend this to anyone who asked for tv shows to watch.