So... I've watched this drama when it came out in 2018 but I decided to rewatch the Korean version that I absolutely love on Netflix and, because a special episode from the Japanese version (that I didn't know of) came out quite recently, I decided to rewatch this version as well before watching this special episode. I remembered not liking this version very much and here is why.

Let's start with the story which is the most important part of why I dislike this version. The Korean version is perfect, well written, the story flows really well throughout the episodes and I understand that the Japanese version had to make some choices in term of changes (not to be just a copy paste of the Korean version - even though it is quite a bit) and in term of plot lines to keep as they have only 10 episodes of 45 minutes each. Some choices were pretty good: they didn't keep the second serial murders case in which Soo Hyun was kidnapped, Iwata learns about the walkie talkie and Oyama by eavesdropping one of the transmissions and Saegusa's mother protects him from his brother's case's mess by giving him to relatives... Other than that, from the very first episode, this version is a mess.

The very first mistake they made was to change the timeline. Right from the start, the story begins in 1995 with the kidnapping case. But Oyama only discovers the corpse of the main suspect 5 years later! Also, Oyama didn't have the walkie talkie in 1995 and started having the transmissions in 1997, which is ridiculous! In the Korean version, the story starts with the same case but the case begins in 2000, the same year Jae Han finds the corpse and he already has the walkie talkie and knows about the transmissions since 1989! These errors lead to two inconsistencies. First, why is Oyama still in possession of a walkie talkie in 1997 when they already had mobile phones and were even seen communicated this way in the drama? At least, the Korean version is logical as in 1989, mobile phones didn't exist and it was their only way of communicating. Second, like the Korean version, the cold case squad was created right after solving the kidnapping case with the help of the transmissions. However, for an unknown reason, in the Japanese version, the transmission first starts in 2010 for Saegusa and the cold case squad is created the same year. And then, 8 years pass, the cold case squad is still in service and Saegusa just joins the team. Again, this is highly illogical as the cold case squad is wanted to be got rid of as soon as possible by the higher-ups and the main villain of this drama especially. How did the squad manage to exist for 8 long years? That would mean that they were successful solving cold cases which doesn't seem like it when we see them again in 2018...

There is another inconsistency created because of this timeline change. Saegusa is seen lonely and kind of depressed at school. This was because in the Korean version, Hae Young lost his older brother and couldn't see his mother because his father took him with him after the gang rape case that involved his brother. But in the Japanese version, there are no reasons at all for him to be sad and lonely because the gang rape case hasn't happened yet and he's still living with his mother and brother who is very much alive. So why doesn't he have any friends at school? I mean, he should at least have one or two friends!

Also, the Japanese version is way too rushed that they forget very important elements that explain the characters' actions. For example, in the first serial murder case, Jae Han suspects the bus driver of being the murderer because he saw him on the crime scene and he indicated him the wrong direction. In the Japanese version, there's no reason for him to suspect the bus driver apart from lying in his testimony as he was not on the crime scene. Moreover, they don't develop the characters' relationships enough. Oyama and Sakurai barely interact with each other (so how is it possible that they fall in love? She doesn't even confess her feelings so what Oyama said after leaving her is inconsistent - again!). Oyama barely interacts with his colleagues as well so there is no team spirit built in this drama and I wonder how he could have back up to save him at the very end. And because they put Iwata as Oyama's chief instead of Nakamoto (who seem to have the same position throughout the years instead of climbing up like in the Korean version - but it's true that only 5 years pass in the Japanese version instead of 11 years in the Korean version), they messed up the relationships between the three characters - especially between Oyama and Nakamoto.

Anyway... There are other inconsistencies in this drama - like the fact that the police have Saegusa's phone when he escaped from them at the hospital (how did they get it?...) and that the cold case squad still exist after what happens with Oyama and the fact that it is not possible because the kidnapping case has been solved in 2000, not 2010... - but I'm going to stop here and talk about another thing that I didn't like in this version... The acting.

It really depends on the drama but I usually don't have any problem whatsoever with Japanese acting. There are some great dramas out there in which the actors are phenomenal. But it is not the case in this drama, sorry... I liked some of the actors like Watabe Atsuro (Nakano), Komoto Masahiro (Iwata) or Kitamura Kazuki (Oyama) for the most part but the Japanese actors in this drama were too much at expressing their emotions. They were always yelling for no reasons and expressing despair, sadness with grand gestures that really didn't fit the situation. Especially in the first episode, during the interrogation of the woman (who is supposed to act in a very cold blooded way), we could clearly see when she was panicking and it was clear from the start that she was guilty. While in the Korean version, the woman barely moves and is only fidgeting to show her panicky state.

About the music, there's nothing much to say apart that the song of BTS really helped the series being known. At least, I like the opening better than the Korean one. They sometimes misused the soundtrack but it is only noticeable in one scene around the end of the drama.

Would I recommend this drama? Absolutely not. Watch the Korean version instead, it is way better in everything.
The Japanese version could have probably been better if they changed the cases they are working on and chose Japanese cold cases instead.