The drama started well in the first season. Initially, it was acceptable that the characters appeared a bit naive since they were just kids. However, this naivety continues into the second season, which takes place two years after the first. The characters seem overly focused on their CSAT exams and returning to their families in safe shelters, despite the fact that almost any young adult would reasonably consider that there might be no 'safe shelter' left in the world, because of the attacks of the spheres.

In reality, none of them seem to grasp that the situation they are facing is dire and that joining the fight against the spheres is crucial. Instead, they act as if the sole thing that matters is their CSAT exams. This might be somewhat understandable if they were 15 or 16 years old, but they were actually 20.

There is not much romance in this drama, but it plays an important role. The unexpressed love between Kim Chi Yeol and Lee Na Ra can be a sigh of relief, as the storyline is pretty hardcore.

While the storyline before the final episodes might feel a bit slow, it builds tension that leads to impactful moments. I was feeling during the end of the 9th episode, that something really tragic was going to happen. But what happened on the 10th, was much worse.

One thing I must say is that there should have been something about the whereabouts of Na-Ra and Ae-Seol in the last moments of the drama.

Overall, I would say this is a pretty good drama to watch. There are valuable lessons to learn, such as the 'fear is our greatest enemy'.

I would recommend watching this UNLESS you prefer dramas with happy endings, as this will not fit that description. It took me a week(literally) to process the ending scenes of the drama. The storyline is tragic, yet very realistic. The CGI is also very realistic. the only things that aren't as realistic are the characters' overcare about their CSAT exams and the 'no shortage of sphere-killing bullets'.