This THISSS.. Thank u so much u put like everything I wanted to say in words. But I'm like too dumb to string a coherent sentence together lmao.
But I agree I think we've all seen this type of character in yaoi for a long time.. but still the timing of his backstory and the MCs being buddy buddy after... Whatever the fuck happened last is a little weird at least.
I think one thing we all can agree on is that were reading this for the DILF and whoever he is gonna end up with.
Goodness you put the words PERFECTLY. I've always thought that su-ah's constant "marking(?)" with the scent is very invasive, if not borderline harassment, especially since Juhyeok have said again and again not to do so.
And that wasn't the only thing that bothers me, it's the fact that he keeps ignoring Juhyeok's Nos and Don'ts, all in the name of he did it because he "love" Juhyeok and that he was only "trying to protect" him. That's.. not what love is? And is it really protection for Juhyeok, or it's just to stroke his own possessiveness ?
I get that Juhyeok is not the brightest and what he asked for was kinda silly, but I thought it was fitting. Su-ah was never really considerate enough to care about him as a person (rather than as someone he's obsessed with, if that makes sense), so why would he care for Su-ah other than for his.. stuff, right? Yet, Su-ah gets offended. Ironically, this is what Juhyeok had to deal with every single day with the scenting thing. But Su-ah couldn't care less about that.
Being protective doesn't mean you have to be inconsiderate or invade the boundaries of the person you're trying to protect, what the hell.

(Be prepared for a yappachino ahh paragraph)
I feel the need to let this out because I find it a bit better to voice my opinion on a story than letting it sizzle any longer. Let me make this CLEAR, I'm not gonna shit or wish death on the author for their creative decisions even if I don't exactly agree with them. At the end of the day it's the author's story and characters.
Now that we've gotten that out of the way
I have a few gripes with Su-ah and the direction his character is going. I don't have to mention the obvious bad things that he did as the commentors have already pointed that out.
Instead, I want to critique the way his backstory was implemented into the story. In truth, it feels very odd in the way that it is placed in the story as the timing couldn't been worse.
I find it a hard time to truly empathize with Su-ah's current self as obviously child exploitation is an awful thing to go through and it's especially not surprising that he'd of course be disappointed about his secondary gender.
But my issues with him as a character still stands as all of what he did against Juhyeok kinda mirrors with the way he was probably viewed and objectified as, an omega. Yes, you could argue that Su-ah cares about Juhyeok but it often times feels like he doesn't care enough about Juhyeok to at least be considerate of his well-being. When I read his inner monologues about Juhyeok I find it be more remoniscent of entitlement and obsession to Juhyeok's body. It's like his personhood isn't even a thought in his mind until Juhyeok beats it to him.
I get that Su-ah is supposed to be the possessive and yandere-adjacent male lead and I'm not yucking on anyone's yum. I fully understand that liking how a problematic character is written does not reflect on irl morals, but I feel conflicted about how the narrative is trying to frame his behavior or even downplay it at times and how he gets out of things scot-free without any real long-lasting consequences.
Maybe it's feels more unsettling for me because Su-ah doesn't take in the consideration of Juhyeok's dreams and goals and how difficult it must be to be in a field probably oversaturated with alphas whilst being an omega, he doesn't seem to understand or even see his reality will always be at a disadvantage for him even though his backstory should at least make him understand why Juhyeok is the way he is and why he cares about his career, but with chapters like chapter 19-20, he feels like any other alpha that wants to baby-trap the MC in favor of their on selfish gain. Juhyeok is biologically tied to Su-ah and it wasn't even by choice, the whole scenting thing strips any agency Juhyeok had over their relationship. As a reader i feel more convinced that Su-ah loves the idea of the promise he made with him rather than Juhyeok himself.
Anyways I think this is another case of a "I'm reading this for the side couples" type of manhwa, since I find their potential to be interesting and I like the artstyle. I'll let this marinate until it's the side couples turn ╮( ̄▽ ̄)╭