This is a hot mess

Even though I ended up liking it over-all (the main character omega is pretty great), there are still plenty of problems here, the main one being that the author has no idea what sort of story s/he's trying to tell.
(spoilers)
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This story is incepted by a rape/blackmail scene that has nothing to do with alpha/omega dynamics, and thus speaks more to the seme's (Jin's) bad behavior than any sort of Omegaverse "instinctual" thing (which is how Omegaverse typically gets away with stuff like this). This is a problem, because it makes Jin out to be a bad person from the get-go. People who commit rapes are not good guys having a bad moment; they're bad guys having a typical moment. Really, Jin isn't any better than the childhood rival who also tried to do the same thing, or the alpha twin who was also told to do the same by his brother. Jin did the exact same thing those guys attempted, but Jin got away with it, and they didn't! If the author wanted Jin to be a good person, yet start the story off with a steamy sex scene, s/he should've just gone with a typical heat/rut circumstance instead, because at least then Jin's behavior can be excused somewhat. In fact, do that, and tie it in with the character development stuff where Jin learns some self control.

And on that note, this story didn't need to be set in the Omegaverse. It didn't really explore any concepts specific/unique to Omegaverse. Shusei could've had a pack of smokes that Jin found instead of heat suppressants. The childhood rival could have intra-family beef with Jin, and drugged Shusei and attempted to rape him that way and the scene would've played out exactly the same. Even the baby bump was pointless at the end because it was like two panels that were completely tacked-on rather than part of the story. If you're gonna set your story in Omegaverse, make it a plot that could only happen in Omegaverse. I hate to keep harping on this, but it's lazy to do otherwise. For a good example of an Omegaverse story that could not take place outside of that setting, go read "Shounen no Kyoukai".

Moving on. In this story, pretty much all of the plot arcs were typical-BL-cliche, where the Omegaverse setting itself was completely forgotten. Yes, one of the twins was an omega, and heat inducers, and yadda yadda. But this is just window-dressing; it doesn't treat the Omegaverse as a setting with any respect at all. For example -- Why is Jin such a good catch as compared to other alphas? It seems like the childhood friend alpha is in a more powerful political position than Jin, and they're cousins, so probably of similar wealthiness. And childhood rival doesn't have a boyfriend/bondmate already, which makes him easier, so why not go after him instead? Sure, he's kind of a weeny, but that's exactly what omega-twin is looking for: a rich powerful alpha to take care of him, who is also pliant. Also, the story never talks about Jin's family in-depth, like how rich/powerful/whatever they are compared to other alphas. There is literally no reason for this omega-twin to go after specifically Jin over anyone else in his entire school full of alphas. Yes! Other than Shusei and himself, he has an entire school full of alphas to choose from to search for a mate! Why does it have to be Jin, other than he's the protagonist? What is even going on here?

In terms of what the story did kind of want to do with the Omegaverse -- there was sort of a thread from the beginning about Shusei needing to overcome the embarrassingness of being an omega, and/or the setbacks of being an omega, or something like this. But his parents / inheritance was NEVER addressed, which was the impetus for how this whole situation came to be in the first place. Also, a big motivating factor of the rape/blackmail plot was that the school was alpha-exclusive, and Shusei's an omega-in-hiding. But when Shusei decides to reveal his second gender, the school just decides to accept it and call it fine, and open itself up to betas/omegas off-screen! This should've been a big, dramatic, on-screen moment, if the author cared about this subplot at all. But, no, there was nothing other than an off-hand mention.

And as far as the childhood rival is concerned, all he wanted was to get ahead of Jin even if by underhanded means. So why drag Shusei, an innocent, into this? It doesn't really seem like his personality to be this much of a bad person. Howabout this instead -- since his parents control the school, he could've just messed with Jin's grades and/or ranking. That would've made for a more interesting arc, since then it could've induced an external change in the rivalry between Shusei and Jin. Then the story could've explored some meaty character questions like do you really win if you didn't earn the winning grade, even if you're not the one who cheated?

Also, the character art was frequently off-model, or the characters were just drawn in an unappealing style, I'm not sure which. The side-views in particular often looked pretty bad.

Somehow, despite all this, I still got the general impression that I liked this one, to the point where I wanted to rate it 4/5 stars. But after all this complaining, I can't really justify more than 3/5. I think my desire to rate it higher is probably because Shusei was an interesting character as far as omegas go. He punched childhood rival's head off rather than lay there and let him rape him like so many other omegas/ukes tend to do. He stood up for himself when Jin tried to alpha-splain him. He took things into his own hands and made the decision to reveal his second gender publicly rather than let childhood rival bully him, or allow his alpha boyfriend to do everything for him. He decisively staked his claim on Jin to omega-twin rather than being wishy-washy for eternity like so many shoujo protagonists. Shusei is very much an admirable main character who brings A LOT to this story, and I wish more ukes/omegas were like him.