This drama had such a good start and theme. I absolutely loved it up until around ep. 12 or something when Ha Na learned about Seo Jin's ilness.

The way she kept on holding onto Robin and feeding into that illusion is seriously damaging and abusive, there's no way someone in real life would do that to someone after finding out they're ill.
She kissed, asked to marry and, as was implied, had sex with Robin who is not a real person and is a result of DID. How fucked up is that?

Ha Na was so selfish that she convinced Seo Jin to live mentally ill for the rest of his life so she could be happy. When that wasn't possible she cried and basically begged Seo Jin to stay ill. She then guilt tripped Seo Jin and Robin for seeking treatment and only accepted Seo Jin when she found out he still had a part of Robin in him.
Everyone else around him also fed into this illusion and nearly made a funeral when Seo Jin was finally cured. What even.

At first I hated Seo Jin's father but after he said Ha Na's behavior was destroying her son and she was the reason he was still ill, I saw that he was the only smart and sane person in this drama. Simply a father(even thought not perfect) rooting for his son's mental health, which is the most important, when not even the psychiatrist seemed to care.