When I first reviewed this title, I gave it a 9. I stick by that number in the case of the first 4 episodes, however as a whole there were bound to be a few issues. Overall I loved this drama and will gladly rewatch episodes, plan on making fanart, and will probably be raving about it to all of my friends for the next few months until the finale hype wears off. Now to get onto the review.

WHO THIS IS NOT FOR:
Those expecting a deep, serious crime drama which makes them reflect on their morality. (strangers from hell)
Those who dislike exaggeration as a character trait or secondhand embarrassment.

~STORY~
If you're reading this review you've probably already heard the premise. I went into this series without it. No synopsis, no trailer, no cast list, nothing but the name of the show. The first five minutes do a really good job of grabbing your attention. And for someone who didn't know anything before the first ep it did a really good job of introducing the main characters, the premise of the show, and the overall tone.
The pacing of events needed some work and the story dragged around midway.
However, that said, it didn't neglect the build up and portrayal of certain psychological issues and injuries.
I wish I could say I was completely satisfied with the execution of this story, however there were logical issues regarding the arcs of a few characters that detracted from the narrative.

~ACTING/CAST~
Yoon Shi Yoon/Yook Dong Shik: I will never be able to say enough about Yoon Shi Yoon. This was the first thing I really saw him in and I was utterly blown away. He is very expressive which seems to be why he was cast for this role. Due to Yook Dong Shik's amnesia and flare for the dramatics Yoon Shi Yoon had to regularly go from nervously giddy, to calm and cold. If you ever get bored just look at how he moves the corners of his lips and eyes. He also has good chemistry with the entire cast.

Jung In Sun/Shim Bo Kyung: At first I thought it was just cause she was the only sane person of the main 3, but as I watched I realized her character is really not for me. The actress does a very good job of portraying officer Shim, but she can't fix the writing for the character. Out of all the things the series prepped well for, it didn't prep for an officer well. There are so many things, especially in the later half, which just don't make sense for her character. She also falls into the trap of damsel in distress. Overall, one of the weakest characters.

Park Sung Hoon/Seo In Woo: Another actor I had never heard of before this. His performance in the first half left quite a bit to be desired and he felt like he knew where he needed to be, what he needed to say, and do, but not how to make it seem quite natural. It was almost uncanny valley of acting. However as the show progressed he slipped into character better and became a real treat to watch. As for the character, he was the most consistent and easy character to understand. A bit flat in the beginning but as they revealed more about him he showed to be much more complex than hatchet swinging serial killer.

Ensemble:
The rest of the cast were pretty fun and had their own agency to them that I haven't seen from many dramas. Even though we didn't know characters well we still could get a general idea of their wants and personalities outside of the main character's life. That is other than the dishonorable mention

Dishonorable Mention:
There is one character, not gonna name names, who has almost no agency and volition of their own. They exist only to aid a single character and don't show any sign of being more than a hollow husk of a person.
I removed a whole star cause this character exists.

~MUSIC~
I JUST WANNA BE BAD!!!
Honestly I love this soundtrack and it's going on a playlist. Besides 'wanna be bad' by the rose, this series sports a few instrumentals. I was actually upset that I couldn't found the sound director in the credits (I'mma have to look for it again). The music fits the energetic dark (ish) comedy tone of the show and really adds to scenes that are already really fun. The opening is very reminiscent of a mix between bond and scooby doo mysteries inc.

~REWATCH VALUE~
The sets are a bit plain but very easy on the eyes, the script episode to episode is decent enough to make a second (or even third) viewing comfortable, and the acting is superb, you may just catch things about characters you didn't realize the first time through. And did I mention the soundtrack yet?

~TL:DR~
Psychopath diary was a pretty well written, well acted, enjoyable dark (ish) comedy. It's really enjoyable the first time through, and easy enough to rewatch. The sound design is fantastic and sets the tone really well.