He wouldn't need to use him if Su Ah didn't scent him for years without his consent but you already know that, you just don't care. The difference between the two of them is Juhyeok is using Su Ah for his own SURVIVAL. He is not doing this because he wants to, in fact he hates that he has to do any of this at all. He NEEDS to use Su Ah. Su is doing this out of DESIRE. Su Ah WANTS Juhyeok and he will do what ever it takes to obtain him regardless of what Juhyeok wants. Su Ah knew he was being used and he consented to it because it benefited him as well. He got to see Juhyeok and planned to close the gap between them and he got to have sexual experiences with him. It's not like the arrangement was completely one sided. But you already know this. You just don't care. And now Su Ah is blackmailing him into a relationship– because that's exactly what he did– and forcing Juhyeok to do things he doesn't want to do AGAIN.
Su Ah was the one who disregarded what Juhyeok wanted (which was to not be scented) their whole childhood. He has ignored and crossed every single boundary Juhyeok has since the fuckinh beginning. And then when Juhyeok does it because he actually needs to survive, he's not taking Su Ah into consideration? The double standard is fucking insane. But you know that already, you just don't care. It's fine to like Su Ah, that's your own opinion. But don't pretend like he didn't start all of this and set this up himself for his own desires.
It seems you people are the ones who haven't read the manhwa or maybe you were too busy drooling all over the screen cuz of suah but that man is in fact a red flag and what he did to juhyeok was way worse than what juhyeok did, you really just keep living in your delusions but he's truly the typical selfish alpha

Dare i say i'm disappointed by suah cuz i understand that he's been holding back his feelings and desire for juhyeok but this whole thing feels so rushed and he doesn't seem to show any respect to juhyeok i mean he's literally doing all that while juhyeok is half passed out on the hard tile floor, he might be cold, it seems his legs are hurting him and he's asking suah to be more gentle and to slow down but he just won't listen like dude calm down, does he seriously expect juhyeok to believe that he actually cares about him when he's doing all that, he's just acting like a typical dominant alpha who can't control himself and doesn't care about his omega's feelings