WAITTT your brain...
It's actually more obvious in chapter 14 (which is still only available in Korean): (SPOILER!! even though the chapter is probably about to come out translated)
Ilwoo went to an abandoned building in the mountains and we see him stab a sack with his knife multiple times, and it doesn't seem like just a display of anger (due to the things happening in the chapter), it seems like he's been doing it to get ready to stab someone. Then after stabbing it seems like he's about to slice his own neck, as if simulating a murder-suicide. Then he says that this isolated place, 'that not even Baekhee knows about', is big enough to 'move around easily' and 'if somebody dies here they won't be easy to find': apart from the somebody dying part, why would you need to 'move around' to kill yourself? Seems like a murder-suicide plan to me.
Sorry for the yapping session lmao
...Why did it take me 14 chapters to realize that Yang Ilwoo's goal isn't just to commit suicide, but to kill someone (Baekhee's father? No?) and THEN commit suicide?? If he just wanted to commit suicide he would have done it sooner, but he seems to be looking for a criminal. The isolated places he's asking to be shown aren't just to hide himself and die, but to bring someone there he wants to kill without being interrupted! I'M SO SLOWWW
So yeah at the time of Baekhee's narration he's probably in prison for murder.
I reread chapter 10 and Ilwoo said that his mother died of an illness while his father died in an ACCIDENT. What if Baekhee's criminal father really had something to do with this incident? I don't think it's too far fetched, Ilwoo came to THAT town with the precise purpose of finding someone who lived there. There are no coincidences in fiction