
The last sidestory(?) was a little confusing, but I think I can imagine what may have happened, maybe. Little 8 year old Nine wanted to meet someone warm, as he said somewhere here. He likely made that wish on a full moon, and hence it was granted - on the moment wherein there is no more danger nor crisis, and their feelings for each other are already clear and determined. If it happened earlier, Melissa might not have been able to give him all that much care due to dealing with crisis after crisis, not to mention how it might impact future Nine's relationship with Melissa. So, he likely replaced older Nine for a moment, until the magic wore off and he went back to his world. After that, little Nine was determined to meet her again - perhaps in a different timeframe, in a path that leads to a similar future? This is what confuses me. I don't think Melissa had to wait for this Nine to grow up, as old as she is, for them to reunite, when they were already together.
If it's an alternate story, universe, and timeline, then we can't guarantee if it's the same "Melissa" that this Nine will meet. So, maybe, little Nine reunited with another version of this reincarnated Melissa, outside of the usual story too, but in a different path? And then, in the previous world, adult nine must've simply thought of it as a strange dream, probably to be told that a younger him had played with everyone in there?

I honestly just thought that the memories were replaced/added to when he was 7-8 years old, because he made that wish for himself I was going to think that ur theory of him being replaced by a different him might be correct but then where would the adult nine go? I don't like that he'll never see the same Melissa so I'm gonna stay blissful and think the memories were added for my sake

Yeah, I was worried about that, but quickly dismissed it - like I said, that's just one theory, after all, otherwise that would mean she's going to be a lot, lot older when they reunite. - My persisting theory that it was just a slight moment for little Nine, to grant his wish... adult Nine would return to take his place as he woke up in his real world.
What he thought was a dream, could very well be an alternate universe. The one thing jarring this pleasant thought is the fact that while there are several story universes, there's only one Melissa.
So, maybe, it's a "link". His young self's wish made it a possibility, his memories afterwards pushed him to move forward, wish granted, and wake up as adult Nine. He experienced a dream-like childhood with Melissa. A mix between dream and reality, youth and maturity.

I know I'm a bit late, but I got time loop vibes.
He made the wish as an eight year old it came true in him travelling to the future and experiencing a day with the person who will love him the most on his life. That is what gave him the hope and resilience to persist even if he doesn't have clear memories. It would also give more reasoning for why in the future he falls for her so hard and fast.
As for where the him of her time is for that day when past him is in the future maybe he just skipped a day because magic, maybe his body was magicked smaller and he Hosted his past self's consciousness, maybe it's similar to whatever happened to OG Melissa just not permanent. Then when little Nine is eventually older it happens again where he makes way for 8 year old nine for a single day because of his past wish which was already granted.

After reading this and connecting everything together, I also think that's very likely the case. That werewolf magic sure is confusing, as well as the mix up of past and present, but it does make sense, thinking about it, that his past self may have faint memories of a kind and caring adult Melissa - I just couldn't fully wrap my head around it because Melissa is meant to be the only one to change the time loop that the Goddess had been setting in motion every time.
This Melissa is meant to be the precedent because the original Melissa from before, the Melissa countless timeloops and stories before, was just the lovestruck, hopeless Melissa who loved her cheating fiance. Which was why it felt like an oddity wherein our present Melissa makes an impact on past Nine, because if he followed his timeline, that'd be a new Melissa, and perhaps not the current Melissa. But yeah, if I can simplify it and apply the theory, then there's no more timeloops - just their story, their past selves, their current selves, and just a strange conjunction between the two periods. To make it even more simple for my mind to unravel: it was all possible due to werewolf magic; there are no alternate future Melissas in this timeline; the new Melissa made it possible for past Nine to meet her present self through their future. There is only one Melissa, and this world's Nine, that made all this possible.
...I feel like I made a complicated matter seem even more complicated in my mind...

While other's mind was immediately centered on something else, the first thing that came to my mind is worry. First, the dragon doesn't remember Taehyuk. Then, Hyo Un remembers him, but Taehyuk nearly dies. Then, Taehyuk forgets, gets abducted, and gets thrown to the sea. Even their past life is tumultous. Just when things were looking up, he's suddenly seized by a strange sickness which made him turn into a child... Considering the seriousness of the problems they faced, I'm just worried something terrible is brewing in the horizon.
Thinking about it more clearly, I am probably worrying too much. Taehyuk now has the orb, and their memories are restored. This could be nothing more than a small hiccup, perhaps an allusion to the fact that Hyo Un was once a child spoiled by Taehyuk along time ago. Maybe, like someone else said, he just wanted to relive his youth subconsciously, and wanted to be taken care of. Hopefully it's not too serious.
I guess what was really off is the timing of when this event took place. It could have happened before, or after... rather than when they're on their honeymoon. But, maybe the author will reveal the reasons why it had to take place now and how it should fit in the story.

... Seeing the update date and the lack of topics under here, it looks like this might be one of those consigned to oblivion. If we're only to base this story on the 3 chapters we have, it doesn't seem to be the type to stand out too much, apart from that premise of an omega lady pretending to be an alpha, and a man who was supposed to be an omega but might be an alpha. Who knows? Maybe someone will pick this up...

...In past life and Current life.
Past life:
Sia: Intensely possessive, Highly emotional, more dangerous.
Heeyoun: Keeps up walls and bluffs his way through (didn't let her know his feelings, didn't let her know the truth about his name , tried to make it appear that he doesn't care for her until his life was nearing its end, which was when he did express that he probably did care for her more than he let on), Didn't want to bear children, Wants to leave her and doesn't want to shackle her, Doesn't wish to cling.
Current life: (as if to make up for their past lives, somewhat...)
Sia: Still possessive, but keeps reminding herself of the contract, and trying to keep her thoughts and emotions under control more.
Heeyoun: Still trying to not to shackle her, still tries to bluff somewhat, but is more honest with his feelings- to the point wherein he wanted to hide his pregnancy for a little longer if only to maintain their contract, Expresses his love for her more (esp. in his youth), Wants to have children.
As if they're trying to make up for their regrets in their past life subconsciously, with Heeyoun being more honest and Sia being (slightly)more in control with herself (although the changes of the boy are more pronounced.) Maybe he also regretted the death of their children in his past life - so rather than see them as shackles like before, he sees them as a new family, that he is capable of taking care of. After all, times have changed - prejudices are less pronounced and his being an actor can rake in money compared to back in those days. The most pronounced thing, though, is probably that unlike his past self, rather than think that she should fall in love and find someone else, he isn't completely against the possibility of that someone being him.

I really liked your analysis, you looked at it from so many angles from past to reincarnations. my first read through I thought after the main story there was an alternate, ancient timeline for them that ended terribly and I remembered thinking I liked the modern version better. Another thing I thought of when reading your comment was how the children called to Heeyoun to help him and were excited about being their children, and even they got reincarnated not blaming him for the past. I wonder what it would've been like if they dreamed about or had glimpses of their past and could fully see the difference or even talk about it. I also like how much confidence he had in his second life in being the omega to her alpha.

It feels like the series has ended in a way that might allow for another volume, but whether it does or doesn't I hope to at least see an extra - nay, even just a single page- wherein he can finally see the restaurant owners' faces fully. I'm happy that the ending hints at him starting to truly move forward.

Visible Age gap? It turns out she was younger than the little boy turned young man! He grew up in a short amount of time!
Horns? He can hide them away!
Messenger appears and turns out hey: Emperor is still alive and is seeking his son, who was a prince!
Family? Yeah, sure there was trouble, but some of them are alive!
Humans and foreigners have yet to enter this territory in a span of centuries, but Saintess is accepted by the citizens so far. (Even if it was because she saved him, surely there should've been one or two onlookers who are worried about a random person entering their realm, even if she saved their prince.) Since there's only few chapters out, we've yet to really see... who knows, maybe there'll be hostile people who despise humans but get convinced in a span of a few chapters/ get defeated by the prince. )
It was like scattering puzzle pieces and seeing them immediately fall into place. I'm not looking for a complicated plot or some intricately made story when I read this, just that it was all so convenient. Still, it's cute and fun, and is nice to read.

And then there's me, who wants to ship Otonari with Toomaki. Haha, although of course I'm not as severe as them. They look like they have boundless amounts of energy enough to power all the light bulbs in their school amd literally worship their favorite pairing. (I know it's mostly exaggerated for gags, but comparing myself to them is more like: Me:"Wow, the official pairing is great but I like seeing these two otaku together. Well, they may or may not end up together since Otonari's heart eyes are lazer focused on their main pairing, and even Toomaki pays more attention to the two." And them: "AAAAAAAAAHHHH the two of them are holding hands to school together while whispering sweet nothings under the cherry trees!!! This should be taken a picture - nay, a portrait of and displayed on a National Museum for generations to appreciate and worship!!!" Or something, so I feel like some random easygoing person who isn't really all that crazy about it, just thinking it'd be nice. )
If those two are to have any chance at romance, considering how Otonari's energy and love is 100% directed at the main couple, it'll probably take until after the main couple's wedding for him to consider any romance for himself, and considering he isn't self-aware, it'll probably be impossible unless Toomaki makes a lot of moves.
Even then, Toomaki's feelings are mostly onesided, and to be frank his type of girl seems to be Kakoi, so it's also likely that it'll be just that: a potential cute ship.

I think Louis should probably change his appearance. Since he'll be living in Daeho's world from now on, and considering his striking resemblance to Sion, a lot of people might mistake them; not to mention how Sion himself might run into them and somehow add to potential insecurities, considering how he acted in the past. Even without dying his hair, maybe Louis can restyle it, and then wear fashion glasses to more efficiently change his appearance outdoors.
That way, Louis will be seen by Daeho's friends and acquaintances as Louis, and even if Sion or his friends randomly appear, his appearance would be considered somewhat different. No doubt Sion might still find a way to stir trouble, but at least the chances of Louis's appearance being a potential subject of trouble is lessened.
Artstyle is cute. The eyes are sometimes too vivid, like they're permanent floursecent bulbs, but it doesn't look too bad.
Story was... ok. It's not too different compared to similar "pitiful ML/2nd ML/Villain finds love in a dedicated reincarnator/transmigrator who will do everything to make them happy." There are a ton of stories with that premise that I've grown to love.
What I wasn't too fond of was the way she left due to the plot changing too much. I understand if she left because of their positions and ages.
I understand if she considered his fixation.
But after changing the plot so much and even being resonsible for healing his curse, she says she doesn't want to change the plot too much? It already changed the moment she stepped in as his maid and warmed his heart. It already changed when he healed him. Did she really want the plot to proceed as normal? Even considering what could happen to him later? There are potentially other ways for her to try and divert his feelings:
Try to let him meet new people.
Make him trust others more.
Be by his side and treat him as a family member, and be firm about it, regardless of how she also feels.
Why leave him and cruelly reject him with the thought that the story changed too much after decidedly changing his childhood?
...Ok, I guess I'm too nitpicky with that tiny detail.
But it's like watching a teenage comedy romance, with the only reason why they're aged up is for them to participate in politics and make big decisions. Pouting, whining, and acting cute are commonplace. It gets a little tiring after a while. It's not even a cute trait - the entire family acted like that 20 years later. I get that there's sappy love, and unchanging relationships, but they really are acting like literal children - even Ibelina, who seems the most mature, is no exception. I'm all for "being yourself", I tend to have childish interests and sometimes act immature but it's like they don't act like children, they ARE children. In the case of the audience with the emperor during his birthday - the emperor might forgive it, and they are 2nd highest, but doing being petty, rude, and childish in front of other nobles? On his birthday? It sets a bad precendent. You can express your displeasure without downright disrespecting him ON his birthday IN FRONT of the nobles - even if it doesn't foster potential disrespect from the other nobles and other classes, even if the emperor doesn't mind, the other nobles might. They may not do anything about it, but it still reflects badly - and in a noble society wherein connections are essential, they basically played jesters of the court.
I don't know, I'm just whining, it all just didn't sit well with me. Nonetheless, I did like the story enough, and as one of the first I've seen of its kind back then, it holds a spot in my memories.