As per https://www.mangago.me/read-manga/prison_dogs/uu/br_chapter-276505/pg-33/ the ones who ended up in room 2 being raped were the ones who tried to kill him. Not enough information to say those were the only ones so I'm not making that claim. It looks like he was using rape as an intimidation tactic to create an aura of fear within the prison to prevent attacks on himself.
Also he was under extreme mental stress. He had no way of contacting anyone outside without putting them in danger. All his phone calls and visits are monitored. So he has to meet and talk to his uncle who is responsible for his mother brother and him all ending up in prison. He can't even get letters. He was attacked multiple times in prison and can't trust anyone. Based on what Jingi said and Heonjae's discussion with his uncle it is possible that this is not the first time Heonjae tried to kill him. Jingi said when Heonjae was transferred to the same prison he didn't know he was sent there to kill him. Also Heonjae directly tells his uncle "I'll do it" and he wants more money than his uncle promised previously. It seems that Heonjae tried previously and Jingi talked him out of it the way he tried in the latest attempt but failed. Anyway he was primarily in survival mode as a target under continuous monitoring who could be attacked at any time by anyone and no communication with the outside world. He was struck in his cell most of the time.
Also he seemed to have issues with handling emotions in the beginning. He was lashing out at Meongil every time he felt an uncomfortable emotion - whether embarrassment or sadness. He is shocked to hear that he grinds his teeth at night. He feels extreme guilt and embarrassment about his past and avoids the topic. He is shown as having become a lot less violent and lot more rational towards the end - maybe because with Meongil he had someone he could trust who would listen. Overall - the characterization is not completely wrong. He had problems even before ending up in prison - a lot of suppressed rage and history of violence. Grey moral compass considering the work he was doing. Then he ends up in prison feeling completely defeated and ready to give up only to be forced to live on as a game for his uncle to watch his suffering on video. It isn't surprising he behaved the way he did.
Also with Meongil - https://www.mangago.me/read-manga/prison_dogs/uu/br_chapter-205758/pg-16/ - this is what happened. He was brought into room 2 to steal the letters.
The flaw in your argument is that you are conflating explanation with exoneration. Everything you listed of Jingi's isolation, his uncle's torment, his suppressed rage, and his survival mode cleary explains the psychological pathology of an abuser. It makes him a compelling, tragic character, but it does not serve as EVIDENCE against the claim of rape.
If a person uses sexual assault as a 'tactical tool' to control their environment, THAT is still non-consensual sexual violation. And when Myung-il negotiates a deal with someone who OPENLY (keyword is openly) USES sexual violence to terrorize the prison, Myung-il is acting under ultimate duress. This is basic knowledge that consent cannot exist in an environment where the alternative is death or isolation. But I admit, Jingi becoming more rational at the end because of Myung-il's presence shows character growth, BUT it doesn't retroactively rewrite the beginning of the story. The evidence CLEARLY shows a powerful tyrant which is ur alpha rapist, using sexual coercion to dominate a helpless inmate, which is, by definition, RAPE. God I hope ur username is a mistake, because that is something.....
Did not say he did not rape anyone and I specifically called out that I'm not making that claim. In Meongil's case I still don't consider that rape because he negotiated an arrangement on his own.
Not exonerating him either. I also called out that he had problems before he landed in prison. His circumstances indicate why but that doesn't make it right. I was just arguing that the character sketch is not wrong.
You are trying to have it both ways. You claim you aren't exonerating Jingi, yet you explicitly state that what he did to Myung-il wasn't rape because of a 'negotiated arrangement.' This is a fundamental contradiction.
And by definition, a 'negotiation' requires both parties to have equal standing and the freedom to walk away. Myung-il is a captive inmate in a cell controlled by a violent alphaa who uses sexual assault as a terror tactic. So when a victim is forced to trade their bodily autonomy to a predator just to guarantee their basic survival or safety, THAT is not a business transaction—it is coerced compliance under extreme duress.
Coercion legally and ethically completely invalidates consent. Saying it isn't rape just because a desperate victim managed to secure a 'deal' to survive his oppressor is the exact definition of victim-blaming. You cannot separate Jingi's violent character sketch from the objective reality that forcing someone into a sexual 'arrangement' through systemic terror is rape, period.
There is no such definition of negotiation. You are making up definitions based on what seems right to you.
I don't think Jingi's behavior is not problematic or that everything he did is right. Also he is clearly shown to be quite callous at the beginning. However I don't use words like rape willy nilly simply because I don't like how an interaction goes.
Accusing me of 'making up definitions' because you don't understand how coercion works is a weak deflection. And a 'deal' made in a locked prison cell with a violent tyrant who uses sexual violence as a terror tactic is not a standard negotiation but also an extortion.
Under every ethical and legal standard in existence, consent cannot be negotiated under duress or fear of harm. Myung-il did not have the freedom to walk away or safely say no. When you weaponize a victim's helplessness and danger to extract sexual acts, it is called rape by coercion.
Calling it what it is isn't using the word 'willy-nilly.' Minimizing a severe, non-consensual sexual violation into just an 'unpleasant interaction' because a desperate victim tried to bargain for his survival is what's actually problematic.
What you are trying to do here is excuse sexual violence by pretending a brutal prison cell is a normal business meeting. You are using word games to argue that if a victim tries to make a deal to survive, it magically stops being abuse.
You are making things up. Firstly a negotiation does not require both parties to have equal standing. In fact it almost never is. There was no pressure on Meongil to agree since Jingi didn't ask for sex. In fact it's clearly shown that he brought him into the room for his stealing abilities. You are trying to find excuses to use the word rape because you don't like the difference in power in their dynamic and want a big enough label for it. However as I pointed out Meongil proposed the deal. It is not a romantic sweet thing because that is not what it is. Does not automatically make it rape.
What you are trying to do here is gaslight the situation by pretending that because the victim proposed a deal to survive, he somehow wanted it. You are trying to separate the "deal" from the fact that Myung-il is trapped in a violent prison with absolutely zero safety.
You claim there was "no pressure" on Myung-il, but that is a lie. The pressure is the entire prison environment. When you are a helpless inmate locked in a room with a violent leader who already uses sexual assault to terrorize people, you are always under pressure. You don't have to wait for them to explicitly ask for sex; you already know what they are capable of.
Proposing a deal to give up your body in exchange for protection or safety is not a normal negotiation. But a desperate survival tactic used by a victim who has no other choice. True consent means having the real, safe freedom to say "no." Myung-il never had that.
Using someone's complete helplessness to get sex from them—even through a "deal" they felt forced to make—is called coercive sexual exploitation, which is rape. Calling it what it is isn't looking for a "label," it is just excusing a predator.

To be honest Jingi's backstory makes his earlier behavior nonsensical. Like..... he straight up did not have to be a rapist, it doesn't even fall in line with his pre-incarceration character. He seemed like a rough guy but not sadistic. Prison could've made him more hardened but not to the point of "Im going to choose this random guy to be my sex slave".
The story could've been that Myeong-Il got close to Heonjae, which led him to making the stand-offish, intimidating Jingi open up to him as well.
The author was just too eager for the sex to begin so both of these complex and interesting characters had to be rapists. A massive disservice to the overarching story thats being told now vs in the beginning.