Knowing the context of his shock after knotting, is making me extra giddy on top of how sp...

omggg what’s the context ?

Please do elaborate

Please only read if you're ok with alot of spoilers!
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Well, it's already been established that Liu had always made a point of going against his nature as an alpha since he deemed it a weakness to utilize its inherent power or succumb to its instincts, so he trained at having perfect control of his pheromones, never using them nor being affected by others' (which he achieved by becoming a Golden Alpha in the process).

Now for spoilers:
All those years of restraint went out the window once he met Yeehyeon, since he felt an inescapable attraction. He started letting out his own pheromones in response to those he sensed coming from him; what he sensed - unknowingly to everyone at that point - are the first signs of Yeehyeon being a special case of a beta person (called Diamond Dust) who induced the ability of a special case Alpha (called Ghost) to turn him from beta to omega through multiple, special knotting sessions.

So the context here is that while Liu never planned nor wanted to - at least initially - not only did he release pheromones and indulged in Yeehyeon's traces of scent, but he helplessly also knotted, unintentionally beginning said changing process from beta to omega. I should also mention that this underlying bond between the two involves a fair share of unconscious - inevitable even - actions. The effects it has particularly on the Ghost can hardly be controlled.

Even though this started as something unexpected, however, how Liu will act from then on will carry a heavy responsibility and implications...

do you have a link to the novel by any chance?

Unfortunately not. You can check novelupdates in case someone has translated it for free. I'd suggest not to pay for unofficial sites that have chapters behind paywalls, not worth it.