SV A/B/O situation where Shen Yuan was an Alpha in his first life.
He would never admit it, but he hated it, too. Like he's a trans egg for at least his secondary gender but he had no wherewithal to process that, plus his health issues meant he was totally failing to meet a lot of the standard expectations for Alphas to be strong and hale and fit and so on, which is part of what drew him into reading masculine power fantasy novels where the protagonists are always peak Alpha males.
Except that he's not really into that, too, because (insert complicated feelings about genderx2 here), so part of the reason why Luo Binghe lit his brain up so much on his first read was that narrative element of perpetual dissatisfaction and existential futility. That he insists is a major flaw because it's too unjust for Luo Binghe to never be happy in all his conquering Alpha male emperor glory.
Airplane reading his comments like, wow we don't have time to unpack all that...
Anyway, when Shen Yuan transmigrates into Shen Jiu he finds that despite his Alpha presentation and his description in the book as an Alpha, Shen Qingqiu is apparently an Omega. Who had been disguising his secondary gender for some baffling reason (dysphoria) that probably had to do with social disadvantages or pride or something (dysphoria 100%) but he's not exactly around for Shen Yuan to ask.
At first the OOC locks mean that Shen Yuan has to keep pretending to be an Alpha (not hard, he's been doing that his whole life so far -- by which he means actually being an Alpha in his first life, of course) but then he finishes the Skinner Demon mission and in the midst of that, Luo Binghe and Ning Yingying get a good whiff of his actual pheromones, after which Shen Yuan figures it's no use trying to keep up the OG's charade.
But this is also strategically sound! Luo Binghe in PIDW did not kill Omegas. In fact several of his future wives arguably did him dirtier than Shen Qingqiu, albeit at a less formative age.
Shen Yuan decides the only path forward is to Omega it up as hard as he can. He's going to have to compensate extra not only for the OG's past abuses and misconduct as a mentor, but also for his years spent "pretending" to be an Alpha, and for Shen Yuan's own completely understandable certainly real difficulties in "pretending" to be an Omega now. It will be really hard for him, all things considered, so he is going to have to be as maternal, gentle, brave, compassionate, and prone to somehow landing in mortal peril with his clothing artfully torn and tears glistening his eyes as the most cliche Omegas straight out of fiction. He is going to mother the protagonist so hard that Luo Binghe won't be able to make an exception for killing him, because everything that saved those other Omegas, Shen Qingqiu is now going to dial up to eleven.
If he commits to it and works really hard at it, maybe it will be enough to stave off Luo Binghe's resentment, and he'll be able to retire in peace after all is said and done.