This is a 10 episode ride of total insanity, where I witnessed some of the most innocent and meanest students choose the worst decisions in the world in an attempt to overturn their immediate future.
What I liked about this? The characters. I admit, I hated almost every single one during the first three episodes, but slowly began to get accustomed to their ways. Every single one of the students at the school are abhorrent in their own unique manner and I would love to meet their parents.

Oh Ji Soo aka Oji, a paradigm outstanding student has a secret: he is abandoned by both his parents. And to make ends meet, he designs a service... which provides "compensated dating" with a catch -- the clients receive exclusive security if things take a dark turn. However, his secret is discovered by his classmate, Baek Gyuri, destroying his careful routine.

Now, let me start off by telling that I had absolutely no idea what was happening in the first two episodes. I just knew that some really shady business had to be going on based on the users' comments that I had read a long time ago.
But, this might be where the drama's strength lies: it's ambiguity.
Ji Soo might either be the worst or the best character based on how you view him. How is he good?
** He accepts clients who sign up and give them protection along with a blacklist of people who are potentially dangerous. He never forces anything upon them if they are hesitant.
How is he bad?
** He is a pimp. Plain and simple. But, he was also, one of the most careless characters I have seen to date. Dude, if you are doing underworld activities, at least be good at it!
I understood his desperation and urgency. Viewing the world through his eyes, he is doing what he could to survive. Except that resorting to crime is not exactly what I would call the best avenue.
Kim Ji Hoon delivered an absolutely strong performance. I couldn't help feeling bad for him at times.

Baek Gyuri... the infamous female lead as someone mentioned in the comments. She has to be one of the most entitled "brats" I have seen onscreen. Why do I say so? Because purposefully messing up with someone's personal life is heinous. I hear the word being "human" and "real" being mentioned. I accept that statement to an extent, but there is a stark difference between being plain bad and committing something bad in a spur of the moment.
She is one of the well written characters. Out of every single one of them, it was she who was the most calculative and manipulative. But, the little cracks that we see through her brave girl façade couldn't convince me 'why' she had to seek out to be a part of this dangerous job. In the end, I felt that she was deceiving herself to maintain her sanity. The manner in which she handled issues was almost flawless and I liked the strange relationship between her and Oji.

The supporting characters, including Minhee and Kitae, were plain horrible. I grew to like Minhee by the end, once she had actually stopped snapping all the time. I adored her friendship with Mr. Lee Wang Chul (He was my favorite character.) It was one of those moments in this series where I felt that genuine care and affection existed. All the remaining relationships portrayed where plain unhealthy or ambiguous.

I couldn't find a single student in the school who was likeable. At least, whoever had screentime anyway. Is it possible that the whole school was full of bullies and gossip mongers? Why were there no genuine friendships? In the end, it was the home-room teacher, the police woman and the dean who has to deal with all this mess.
The soundtrack was awesome. I loved the main theme "Speak for Yourself".

I do not know how much of the events depicted in this is possible in real life. But, an elder sister I knew did tell me about a thing like this in college where students solicited for money-- often leading to awkward and unpleasant encounters when they encounter their own kind.

I would suggest this to anyone looking for some thrill -- it was slightly dragging and slow upto episode 5, then managed to hold my interest during the last few episodes. Unfortunately, I had high hopes for this one, but I found it a tad bit predictable, considering that the characters kept digging holes the size of Mariana Trench every other episode. The ending was quite fitting, personally. A second season might ruin the effect of the first, which I felt, wrapped up quite nicely.