I gave this an 8 rating for the mystery and "who done it" value. However, I didn't particularly like the K-drama as a whole. It centers around a group of very close friends that were in college together and now are in their 40s and living in the same town. The series basically has an adult theme centering around unsolved murders, extortion, rape date drugs, obsessive old love, adult film director and actresses, getting duped by underage scammer, paying scammers to convict friend's wives into bed to trick them into getting caught so they can have a chance to get their old girlfriend back, innocent children involved, etc - all the while in college boys protecting boys and later in their 40s men protecting men. Each person has their own personal story as to why they are the way they are and is divulged slowly. The 16th episode you find who the real recent murderer is. The 17th episode is an add on to divulge the final update of each of their personal story ending. I was really disappointed in my favorite character Jo Hyung-Woo's update on his personal story. How ridiculous. I think the script could have been better.
