I have watched this drama on my first k-drama spree. And since, many many others were watched but this one holds a very special place in my heart.

First, the storyline is very different from what you'd expect in a k-drama. The screenwriters tackled mental health in a fine and interesting  way.
The conversations between the characters have depth, meaning, and come across as "natural" and not scripted or over the top, as usually kdramas do.
The characters felt like real humans, with their raw emotions.
Even talking about sexuality in a way that felt reel to me, and not timid or romanticised way. I was really surprised by that.

This si definitely a must-recommend drama, with brilliant actors and storylines, and especially how it all goes down with twist.