On most of the parts I do agree with the comments here, the 1st half of the show is indeed amazing and 2nd half went quite expectedly downhill because they added too many plot twists which obviously created more loopholes and illogical actions. I quite like the chemistry the cast actors had for the show not just the main leads.

1st, I like that they kept the romance at a right amount because it is focused on action and thriller while looking for the murderer hiding behind everyone though I'd say it was kind of obvious to me who had the strongest motive. So thankful the story isn't like most typical K-suspense dramas.

2nd, I really like how they kept us guessing what actually happened in the clique of friends that caused the brother's death. They honestly did a great job ensuring audiences follow the story's flow of thoughts and their logic/hints behind every scenes shown.

3rd, I really kinda hate Kwon Se Jin's character... It feels like he's not even needed in the story even though his existence should hold a lot of importance to resolving the mystery. The problem lies in the character that he is actually Ok Chankyu's love interest, yet he gave the least effort in trying to return his lover the justice while the sister works her ass off looking for details even though she didn't know what her brother faced in school. To me, it seems that Kwon Sejin didn't even bother to observe what his lover went through when they are so close and only assuming things as "truth" which ended up influencing FL's thoughts and decisions...

lastly, get that the ending isn't the best for most people but I like how the girl (victim) repaid the kindness by asking the entire school to protect the ML through the text message, it was honestly so satisfying and heartwarming at that moment. Even the police decided to take a step back which was undeniable they understood the students' wish to do justice to the ML who deserves kindness and protection and the person who truly deserved punishment.