Just a heads up: if you don't like the types of shows where each episode has a unique plot, and the "main" storyline is unraveled bit by bit throughout each episode, you probably won't like this one. The background of the main characters are fully addressed at the end; I think it's worth your time though! I thoroughly enjoyed all 16 episodes :)

Something some people don't realize about this kdrama is the fact that the main focus is the topic of how suicide is not one's only option when they're suffering, not Koo Ryeon & Joong-Gil's history. The writers' target audience is people that are facing hard times, where the writers are hoping that they would try grasping onto hope and waiting for better days to come; the plot is just a bonus.

The formatting of this drama is quite different than a regular kdrama, where the plot/backstory o the main characters aren't the main focus, but the very sensitive topic of suicide. I saw other people in their reviews complaining about how the storylines were very uniform and every episode was basically formatted the same, and I do agree with that, but I think that the unique experiences and lessons each individual episode holds makes watching every episode heartwarming in their own ways.
Each episode features a different person, in a very different situation from the last. From animals to celebrities, the writers were able to address many of Korea's most pressuring stereotypes that may cause someone to feel like they don't belong in this world. Though some may think that the amount of diversity between the characters is overwhelming, I think that the heterogeneity of the characters' situations really connects into the real world very well.