For those confused by Chapter 62

I noticed a lot of people saying they were confused by chapter 62; specifically, that scene with the recording device. I went a bit off topic in places, but I hope this helps to clear things up.

That device was used by Seungbae, the young detective, to secretly record Sangwoo while he was in police custody between chapters 33 and 34. The information in the flashback is new to us, the audience, because the scene took place at a time when we were watching Bum. You can actually see the recording device fall out of the car in chapter 35 when Seungbae violently pulls Sangwoo out of the police cruiser.

The author is making the case here that Suengbae never listened to the recording prior to chapter 62. It seems hard to believe that he didn't listen sooner, but perhaps the trauma caused by being fired by Chief Kwak, the old detective, caused him to forget? As we've seen in previous chapters, Suengbae has been haunted by his failed attempt to prove that Sangwoo is guilty of murder. He literally has visions of Sangwoo taunting him, so needless to say, the kid is often on his mind.

The recording itself is of Sangwoo switching from what appears to be fake crying to an evil, maniacal laughter. While this audio has nothing to do with the murder of Chief Kwak, it does serve as a sort of vindication for Suengbae. The recording can't be used as evidence for anything, but it does prove to himself that he wasn't wrong about Sangwoo being a sociopath.

In chapter 60, we saw Chief Kwak reflecting on his decision to fire Suengbae back in chapter 35. The young detective tried to explain why he thought Sangwoo was guilty of killing Min Jieun, but the chief wouldn't listen. Prior to chapter 60, I don't recall the chief being personally involved with the investigation. Whether he felt guilty for not listening back then, or he simply decided it was worth looking into since the case had gone cold, Kwak decided to visit Sangwoo.

During their car ride, Officer Lee told Suengbae that Chief Kwak seemed unusually focused on trying to solve the murder of Min Jieun, despite the fact that it was Lee's investigation. After hearing the audio, Suengbae pictures the chief's body being set up to look like a suicide by Sangwoo. This scene is strictly of the detective's imagination. The only thing that the audience knows for sure is that the chief is dead and that it was staged to look like a suicide. I think we can safely say that he was killed by Sangwoo (or possibly Bum), but the detective has no way of knowing this. Despite the lack of proof, he seems pretty convinced that Sangwoo is behind the chief's death, and from the way chapter 62 ended, it looks like he's finally returning to the case, albeit informally.