It is easy to understand Su-ah's feelings for Doyoon because he knows what he wants from h...

It is easy to understand Su-ah's feelings for Doyoon because he knows what he wants from him.

With Doyoon, while it also seems clear-cut at first, upon reading more I needed to understand him.
He hates Alphas, yet he dates Alphas later; and the terrible, trashy types, too. Does he attract those types? Is he attracted to those types? Or is it simply that all those he was attracted to turned out to be terrible? So I can only embark on a journey of understanding Doyoon with my own interpretations (that may be wrong or very wrong, but I just like to unravel it as I go).

Considering this is an omegaverse story, I have to first understand his position. From a young age, he thinks of omegas as cute and helpless, and alphas as big and strong. As a beta, he naturally considers himself as simply in the middle - in other words, omegas to protect, alphas to watch out for, whether in a good or bad way.

So naturally, he was completely oblivious and unintentionally dismissive of his childhood friend's affections, not to mention how he is just this adorable little brother type who is an omega. Someone to protect and cherish.

On the other hand, his hatred for alphas may not be so much as hating alphas, but hating those who use their status as an alpha to act cruel. His type, from what I gather, is the big, strong, assertive alphas that would properly look at him as a beta and pick him. Unfortunately, the ones he dated so far were all the types who DID take interest in him, but while they were big, strong, and assertive just like his preference; they were also all interested in omegas more than betas, and just wanted to perhaps "try him out", like the men in some stories I've read wherein they date guys, but later find out they're not into it/they were two-timing/ never took the relationship seriously etc.
In other words they liked omegas, but wanted to try it out with attractive and nice betas (like green-haired dude. He's one of them, hence after I paid attention to this bit it came as no surprise that Doyoon also found him somewhat his type.)

So why did Doyoon suddenly get attracted to someone who seems to be the opposite: cutesy, clumsy, and very dependent on him? Because if we think about it, he still fits into his type: big, strong, and assertive. The only difference that made him even more special, perhaps, is the fact that this one truly, dearly loves him and not as a substitute for an omega.

I did think that with Su-Ah's (somewhat foolish but understandable) decision to pretend being an omega, it wouldn't be all that impossible if he tried to emulate what he thought was Doyoon's type - becoming a red flag type. Imagine if Doyoon came across a Su-Ah who flirts and dates with people left and right, while also being sweet and assertive towards him, like the guys he dated before... Not only will Su-Ah completely lose his chance, but he might actually disappoint or even anger Doyoon completely, because a lot of unnecessary heartache had to occur just so that he can get what he wanted. If, in spite of that, they do get together, Doyoon would feel unstable with him like he felt with his exes, and Su-Ah might feel reassured that he's Doyoon's type and repeatedly hurt people, and even if he mends his ways there might be a tremendous fracture on trust that will ne veey hard to overwrite.

So it's a good thing he's not decided to take that path, and instead smother Doyoon with love, to make up for what his exes did to him.

That's also probably why he said he's his hyung's omega and alpha - he is cute, sweet, and needs reassurance, but he is also assertive, "secretly"(?) possessive, and very much honest with his desires. (Of course, these are simply stereotypes, but I'm referring to Doyoon's and Su-Ah's perspective in here) Besides, it's very clear he also loves the cute side of Su-Ah. Ot would be ridiculous to see Su-Ah change into someone else at this point, so he'll still be that sparkly, sweets-loving crybaby sweetheart. What Doyoon truly wanted, perhaps, is not a red flag alpha boyfriend, but possibly someone he could depend on, and will choose him, despite his being a beta.

Why did I need to do this? Because I also wanted to understand what Doyoon might've seen in those hooligans, and what he later sees in Su-Ah. I guess I wanted to reassure myself that Doyoon loves Su-Ah dearly as well, beyond just simply treating him well and compromising for his sake and for his happiness. I also wanted to see how I can properly link Doyoon's childhood thoughts, his past thoughts, and his present thoughts to make a long scroll of how things were and how they got to be. It's not necessary, but it's a pretty fun activity as well (occasionally, because for some stories these would be mixed with resentment and/or tears, like with unexpected tragedies and heartrending betrayals etc.)