after watching episode 9 it's quite telling that Joonmo and Euijung are growing attached to Kichul - Specifically in Joonmo's case. He's far gone into the criminal world and we saw a glimpse of that during the brutal fight scene in episode 8. another argument that i have about why there's no going back for Joonmo is because throughout his life people have been looking down on him because he's poor and is the son of a druggie - to the point that Euijung's family is looking down at him because he's not successful in life and this really tears his confidence down. him being one of the frontmen in Gangnam Union will bring him nothing but the complete opposite of what he had before - money, business success and most of all RESPECT!
all i know is that Joonmo will not be how he was prior to joining this infiltration case - he's witnessed way too much madness, emotional psych, verbal abuse and unfathomable beatings, like babes, he's gone and there ain't no way in hell he'll live a normal life as a police officer again and that with Euijong at that! on the topic of their marriage, i don't see it last. after what just happened in episode 8, the emotional trauma and absence plus the awareness of them cheating on each other... sure, they might both be cordial in the end but that'll only be as friends because i've a hard time to believe that both Joonmo and Euijong can be able to live a happy ever after life and grow a family together after everything they've been through, like it doesn't make any logical sense in my opinion.
this might be a hot take but i don't think Kichul will end up in prison (but there's still a high chance that he does lol). i don't think he'll have a sob ending. let me track back to what i said before about Joonmo officially joining Kichul's gang, because it's a high possibility, and completely leave his police life behind - as we all know, both Joonmo and Kichul are emotionally devoted to this drug business and there's no going back for either of them. they'll join hands as a partner-duo and run the entire Gangnam Union. if Kichul ends up in prison Joonmo will tag along and join him, as we've seen him do numerous times going out of his way to risk his life for Kichul despite it not being crucial for him to do so, and this is a sign that he's growing attached to Kichul and this business.
y'all have brought up your predictions about who dies from the main 3. my first bet is on Euijong, and she'll be killed by one of Kichul's men. we've seen throughout this series run that a few of his men are irritated about her presence in Kichul's life and how he easily drops important meetings just to go on dates with her. Euijong will be killed off either by Jeongbae or Heeseong as them two are the most irritated and have the most probable chance to kill her just to get rid of her as they think she's a distraction for Kichul and their business. if this happens, Euijong dying i mean, it'll probably add another fuel into Joonmo staying in Gangnam Union and help the drug trade not being found out by the cops - all i know is that he won't go back to be a police officer if she dies and to continue to deal with the bullying of her family.
i might be wrong but this is the impression that i've gotten up till now.