I anticipate generating a lot of anger for what I'm about to say, but it isn't fair to Kyujin's character to leave it unsaid amidst all the Kyujin-hating going on.
(spoilers) . . . . . . . . . . . . . . . .
Do people forget that Doyeol is an abusive rapist with anger issues and is an obsessive, manipulative gas-lighter? Let's make a list!
* Doyeol acting crazy possessive in chapter 1 just by the idea of Kyujin going to college with other theoretical guys who might find him cute. Huge red flag here! Imagine if some guy your daughter or little sister was dating said that to her.
* Doyeol rapes Kyujin violently in chapter 2 for no reason but his own insecurities, and for some reason its conveniently forgotten? Don't give me no crap about a kiss; this is not equivalent at all. AND the two (Doyeol and Kyujin) weren't even in any kind of official relationship at the time (a later chapter made a big deal about the rings), so Kyujin had every right to do whatever he wanted, even if it was inconsiderate.
* Doyeol frequently exhibits serial-abuser behavior by taking advantage of Kyujin's confusion over his romantic feelings for Jimin and his feelings of obligation to Doyeol as his only surviving blood relative to either force Kyujin into sex, or force him to come back into their comfortable, unhealthy, co-dependent relationship.
* More serial-abuser behavior when Doyeol blows up at Kyujin and says really hurtful things, then comes back the next day being all kind and sweet and caring and making him dinner and all that. This is a huuuuuuge red flag. HUGE.
* Doyeol reads Kyujin's text messages from Jimin, responds to them in whatever way was convenient for him without consideration of Kyujin's feelings at all, after fully admitting and accepting that Kyujin was in love with Jimin and not him. He never admits to this invasion of privacy and Jimin/Kyujin never seem to figure it out.
* Additionally, the times where he pushed Kyujin into sex when he was clearly not interested (in the shower, the last chapter, etc).
* The shower scene was particularly ugly because you could see the step-by-step process that Doyeol went through to manipulate Kyujin further and further into increasingly more sexual things to get his way against Kyujin's will. Awful.
* In the final chapter scene where they return to the old apartment, Kyujin says no ("what're you doing? we can't do this anymore") even if its in a wishy-washy way, but Doyeol pushed him into sex after that anyway. Did everyone conveniently forget that Doyeol is married at this point, and Kyujin and Jimin are only dating? How in the heck is Kyujin's crime here worse than Doyeol's?
Now for Kyujin's list of screw ups:
* Not being clear and firm with Doyeol about how he felt about him once he had figured it out
* Kissing someone else casually when he and Doyeol have been in a carnal relationship even if their relationship was undefined/unofficial at this time (but he did tell him about it voluntarily); this was extremely inconsiderate
* Not moving out immediately upon realizing he and Jimin loved each other, even if Jimin was going to be gone for a year
* Buying the rings for he and Doyeol at a time when he obviously didn't understand his own feelings, which ended up setting expectations that would come back to bite Kyujin in the butt later
* Not telling Doyeol about running into Jimin after Jimin came back from 'murika. Hiding things is never good.
* Both of them get a ding for what happened in chapter 25, but Doyeol screwed up more because he was married and pushing hard for it and Kyujin was pushing back and did tell Doyeol no, even if in the most noncommittal way imaginable
Jimin I can't really say much about because he was immature and did some minorly crappy things as a kid before he left, but acted like a respectable adult when he returned. He seemed like the one most screwed over by the end of the story. Although he did say a few serial-abuser lines toward the end there that got me a little concerned that Kyujin was a psycho-magnet.
Anyway.
Kyujin from the start was clearly portrayed as confused about his feelings. First of all, their parents died when the boys were young and they only had each other for a long time. This situation is a perfect setup for emotional dependency without romantic love (Kyujin), or an emotional dependency with an irrational obsession (Doyeol). However, it is stated early on that despite their relationship, Kyujin doesn't love Doyeol as much or in the same way that Doyeol loves him. Even Doyeol admits he understands this, so he has no business getting upset when Kyujin does find someone he feels he loves in a romantic way later. Sorry it wasn't you, bud, but life is like that sometimes.
Furthermore, because Kyujin's never felt any kind of romantic feelings for anyone before, he seems to be having trouble telling his feelings of romantic love/lust for Jimin apart from his feelings of emotional dependency toward Doyeol. Of course Doyeol uses this to his advantage throughout the comic to manipulate Kyujin into feeling guilty and eventually doing what he wants (including chapter 25).
Lastly, when you've been in a given situation for so long, it's hard forcing yourself to break away from it even if you know it is the best thing for you to do. This is as true for Kyujin leaving Doyeol as it is for a person leaving a job they've held for a decade. Riddled with guilt, the unknown is scary and change is scary too. Anyway, this is a very common problem for people in abusive relationships. Kyujin is the victim of emotional abuse and manipulation, and it's hard for him to pull away from it because he has been manipulated into second guessing his actions. This happens to (mostly women) all the time in the real world here; cut the guy some slack.
tl;dr
The bad person in this comic is Doyeol. He's a violent, abusive manipulator and deserves everything he gets. The best thing for everyone would be for Kyujin and Doyeol to go their separate ways permanently, and for whoever Kyujin ends up with (be it Jimin or no) to be aware of how abusive his past relationship was and to help him resist the temptation to return to it. Because it will always be there, nagging him in the back of his mind, guilt-stricken and alluring.
So much hate for Kyujin, it's kind of sad really.
I anticipate generating a lot of anger for what I'm about to say, but it isn't fair to Kyujin's character to leave it unsaid amidst all the Kyujin-hating going on.
(spoilers)
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Do people forget that Doyeol is an abusive rapist with anger issues and is an obsessive, manipulative gas-lighter? Let's make a list!
* Doyeol acting crazy possessive in chapter 1 just by the idea of Kyujin going to college with other theoretical guys who might find him cute. Huge red flag here! Imagine if some guy your daughter or little sister was dating said that to her.
* Doyeol rapes Kyujin violently in chapter 2 for no reason but his own insecurities, and for some reason its conveniently forgotten? Don't give me no crap about a kiss; this is not equivalent at all. AND the two (Doyeol and Kyujin) weren't even in any kind of official relationship at the time (a later chapter made a big deal about the rings), so Kyujin had every right to do whatever he wanted, even if it was inconsiderate.
* Doyeol frequently exhibits serial-abuser behavior by taking advantage of Kyujin's confusion over his romantic feelings for Jimin and his feelings of obligation to Doyeol as his only surviving blood relative to either force Kyujin into sex, or force him to come back into their comfortable, unhealthy, co-dependent relationship.
* More serial-abuser behavior when Doyeol blows up at Kyujin and says really hurtful things, then comes back the next day being all kind and sweet and caring and making him dinner and all that. This is a huuuuuuge red flag. HUGE.
* Doyeol reads Kyujin's text messages from Jimin, responds to them in whatever way was convenient for him without consideration of Kyujin's feelings at all, after fully admitting and accepting that Kyujin was in love with Jimin and not him. He never admits to this invasion of privacy and Jimin/Kyujin never seem to figure it out.
* Additionally, the times where he pushed Kyujin into sex when he was clearly not interested (in the shower, the last chapter, etc).
* The shower scene was particularly ugly because you could see the step-by-step process that Doyeol went through to manipulate Kyujin further and further into increasingly more sexual things to get his way against Kyujin's will. Awful.
* In the final chapter scene where they return to the old apartment, Kyujin says no ("what're you doing? we can't do this anymore") even if its in a wishy-washy way, but Doyeol pushed him into sex after that anyway. Did everyone conveniently forget that Doyeol is married at this point, and Kyujin and Jimin are only dating? How in the heck is Kyujin's crime here worse than Doyeol's?
Now for Kyujin's list of screw ups:
* Not being clear and firm with Doyeol about how he felt about him once he had figured it out
* Kissing someone else casually when he and Doyeol have been in a carnal relationship even if their relationship was undefined/unofficial at this time (but he did tell him about it voluntarily); this was extremely inconsiderate
* Not moving out immediately upon realizing he and Jimin loved each other, even if Jimin was going to be gone for a year
* Buying the rings for he and Doyeol at a time when he obviously didn't understand his own feelings, which ended up setting expectations that would come back to bite Kyujin in the butt later
* Not telling Doyeol about running into Jimin after Jimin came back from 'murika. Hiding things is never good.
* Both of them get a ding for what happened in chapter 25, but Doyeol screwed up more because he was married and pushing hard for it and Kyujin was pushing back and did tell Doyeol no, even if in the most noncommittal way imaginable
Jimin I can't really say much about because he was immature and did some minorly crappy things as a kid before he left, but acted like a respectable adult when he returned. He seemed like the one most screwed over by the end of the story. Although he did say a few serial-abuser lines toward the end there that got me a little concerned that Kyujin was a psycho-magnet.
Anyway.
Kyujin from the start was clearly portrayed as confused about his feelings. First of all, their parents died when the boys were young and they only had each other for a long time. This situation is a perfect setup for emotional dependency without romantic love (Kyujin), or an emotional dependency with an irrational obsession (Doyeol). However, it is stated early on that despite their relationship, Kyujin doesn't love Doyeol as much or in the same way that Doyeol loves him. Even Doyeol admits he understands this, so he has no business getting upset when Kyujin does find someone he feels he loves in a romantic way later. Sorry it wasn't you, bud, but life is like that sometimes.
Furthermore, because Kyujin's never felt any kind of romantic feelings for anyone before, he seems to be having trouble telling his feelings of romantic love/lust for Jimin apart from his feelings of emotional dependency toward Doyeol. Of course Doyeol uses this to his advantage throughout the comic to manipulate Kyujin into feeling guilty and eventually doing what he wants (including chapter 25).
Lastly, when you've been in a given situation for so long, it's hard forcing yourself to break away from it even if you know it is the best thing for you to do. This is as true for Kyujin leaving Doyeol as it is for a person leaving a job they've held for a decade. Riddled with guilt, the unknown is scary and change is scary too. Anyway, this is a very common problem for people in abusive relationships. Kyujin is the victim of emotional abuse and manipulation, and it's hard for him to pull away from it because he has been manipulated into second guessing his actions. This happens to (mostly women) all the time in the real world here; cut the guy some slack.
tl;dr
The bad person in this comic is Doyeol. He's a violent, abusive manipulator and deserves everything he gets. The best thing for everyone would be for Kyujin and Doyeol to go their separate ways permanently, and for whoever Kyujin ends up with (be it Jimin or no) to be aware of how abusive his past relationship was and to help him resist the temptation to return to it. Because it will always be there, nagging him in the back of his mind, guilt-stricken and alluring.