Good eye. Never thought about it before, but this lines up with what I recall about VH's development - translation efforts started around 2009-10 (I only found the game itself around 2012-13, when they still had their old wiki up) but from what I've heard, actual development on the game began a couple years before that among anons on 2ch - as far back as 2005 if I'm not mistaken. And guess what, Black Cat's manga run ended in '04 while its anime came out in '05, while To-Love Ru ended in '09 and To-Love Ru Darkness (the spinoff which focuses on Yami/Darkness) started in '10.
I'm not privy to the details (and I would be astonished if the Japanese archives from 15+ years ago are still around & viewable in any capacity) but I believe Omoidashiwara must've gotten involved around that time. He couldn't have created Serena that long after the start of VH's development since she was the second playable character, the one who got the second-most content after Nanako, and while it's been ages since I touched anything VH I'm reasonably certain the Katteban version which he made to focus on her exclusively was already around by '12-13. Yeah, the timeline does definitely check out now that I think about it. I guess the blonde hair + red eyes combo on a loli was a real winner for him.
I will say that's pretty impressive. This means the dude's been working on something involving Serena for 15+ years straight at this point, almost 20 even (VH from a little after 2005 probably, and then the last Katteban update seems to have been in around 2018 - would make sense if he switched to developing VP around then) and has gotten to make a tidy profit off of it at long last, if the sales figures on DLsite are to be believed. He's earned every yen for sure, the pixel art in this game is among the best I've ever seen as far as indies go, and while the story & characterization isn't the most sophisticated in the world I think he did a pretty good job overall of making Serena likable.
I distinctly recall that in VH she was much more of a stereotypical haughty aristocrat who was condescending/dismissive toward commoners (including Nanako on the very rare occasion that they'd interact) even if she wasn't being actively malicious, probably so the player wouldn't feel too bad for tossing her into H-scenes, so VP Serena came across as a pleasant surprise. This consistently polite, good-natured and non-classist girl got me to root for her and to try to get her to the finish line a pure virgin.
I'm sure Omoidashiwara is going to want to take a break after this, probably work on a new game or two before returning to Serena's adventures, and I wouldn't blame him one bit for it considering how much work he's put into VP. But I hope he does come back 'round to make a VP2 at some point - I'd love to be able to have greater interactions with Nanako & the other VH heroines beyond the tutorial section next time. It'd be neat to have a wholesome love interest with more of a backbone than Tim too, whether he be a 'Prince Charming' sort like the noble boy she could bang in VH (and can actually be seen dating in a cameo on a Nanako playthrough), someone from the Grazia Bank also in VH, a lowborn serving boy from her household, etc. Because right now, the 'consensual sex' tab in Serena's diary just seems like a bad joke.
Failing that, some DLC to finish & implement unfinished content like the corruption system, at least, would be nice. I miss the open world-liness of VH and it's a pity that VP only allows the player to more freely roam its maps so late into the game (after getting the quest for 10k it seems) but I 100% understand why Omoidashiwara went in that direction, a narrower but more polished experience with an actual ending(s) always trumps a bloated & unfinished (arguably un-finishable even, whether by one dev or an entire revolving-door team of them) one in my book. Better to be narrow as a puddle but as deep as the ocean than the other way around.