A few personal thoughts to share: I'm quite amazed that almost nobody predicted this outcome, given the manga has, from the very beginning, been playing it super straight, what you see is what you get. I think I recall like 3 or 4 comments from the hundreds that said this is how it would play out (congrats if you're one of the lucky ones!).
Of course, it's really hard to imagine the exact outcome of any story, especially a mystery (I didn't guess this outcome when I read it myself, so I don't get any cookies either). But what stood out to me was how most people were going so far off course with the theories and purposefully avoiding the most basic of interpretations (ie they're simply cheating as presented in the story, which would then lead to the twist of only Kyouko cheating, so you'd have been half right if you just assumed the basic), that I was genuinely somewhat anxious I'd be letting folks down with the very simple conclusion, even though I didn't even write the story and am just translating it lol.
Naturally there is purposeful misdirection to complicate it, but overall the plot has not really veered too far off course from what it has initially presented to the reader, so it's interesting that some really complex theories have formed around it.
Perhaps this is the result of a somewhat unintended demographic reading this. Many people really focused on the mystery angle and drew complex narratives in the comments (totally understandable, who doesn't love to theory craft and try to identify the red herrings/misdirection), while the manga is more of a by-the-books shoujo/josei, and to me it's always been primarily a story about Mahoro's emancipation, not just a cheating mystery (even if that's the hook), so I always took the mystery at face value when I read it and simply put myself in Mahoro's shoes and assumed her worldview.
Another thing is that a lot of stuff is glossed over. Like yeah, this sting operation probably isn't very smart if you analyze it, but the goal of the story is clearly elsewhere so it doesn't bother really making everything perfect, just enough to preserve suspension of disbelief, which in turn makes the scene more spicy like in a TV drama.
Same with the timeline, you don't really see much of Mahoro's life outside of when she's investigating the affair (to the point where some folks even wondered if she worked at all, despite that being established in chapter 1, just not shown). Did you notice several months have passed since the start of the manga? Go back and read it, its mentioned in a throwaway line. We started in November and it's now somewhere around spring/summer. So we're really only shown the very important moments, all the rest of the story is trimmed and downtime abridged. The author has a plot to tell and isn't really concerned with the stuff around it (only to the point of maintaining suspension of disbelief).
Other things are what I suppose I would describe as "male-centeic takes in a female-centric work" for lack of a better expression. This mainly came across with regards to the perception of the male characters in the series.
For example, since chapter 1 some people have been defending or at least presuming Rei's innocence (either that he's not cheating or even that he's actually a nice guy and we're dealing with an unreliable narrator/perspective), whereas the jp audience unanimously called him a piece of shit since chapter 1 and most didn't even assume he wasn't cheating, since there are more signs pointing to it than not like the letter, the first pages of the manga, and the title/synopsis (plus his demeanor/behavior but those can always be misinterpreted).
If you take the story at face value, and especially if you're a woman who has dealt with people like Rei irl (they're... surprisingly more common than you think), that's the conclusion you invariably arrive at. The author, a woman herself, when writing to an audience also comprised mostly of women, clearly wrote Rei with those presuppositions in mind. It's a given that Rei is a bad person because his behaviors are so well known and common among the intended audience that the tidbits Mahoro mentions alone are enough to paint almost the whole picture. But in these comments a lot of people much prefer exploring alternative possibilities and presume Rei's innocence to a certain extent, if not entirely. Not to say who's right or wrong in this story's case (I ain't spoiling), just pointing out the stark difference in perception.
Another difference was the reception of Haruto. I was actually quite shocked so many people didn't like him because, when I first read these chapters, he just seemed like a goofy guy who liked to lighten the mood and was presented as such. Some commenters were even accusing him of taking advantage of Mahoro when all I saw was the two having completely reasonable banter (Mahoro even smacks his hand when he gets too close, clearly consciously establishing boundaries, which he respected). He hasn't pressured her to do anything or tried to put her in any awkward spots, he's just accompanying her and keeping things cool, something she explicitly appreciated because it helped her be more rational and less tense (many people overlooked the fact he dispelled her fears of Rei being in bed with Kyouko, saying Rei is unlikely to rent a suite just to sleep with a woman, so he at least on a surface level has her best interest in mind and is not taking unreasonable positions for personal gain). But hey, different strokes for different folks, if you don't like him that's that.
Though I do wonder if these commenters would react the same way with the genders reversed, considering the sheer volume of manga with horrible, toxic women that are full of "I can fix her/she can ruin me" comments. Not that I am criticizing those series' or comments' existence, just pointing out the polar opposite attitude when it's a man being... Just kinda silly(?) around a woman (it's particularly funny when Haruto is quite ordinary all things considered, unlike more tropey shoujo heros. Being kind to someone is a baseline, not a trait reserved for prince charming only). I don't want to go as far as saying it's insecurity projection, but it is a peculiar shift in views.
I don't really know where I'm going with all these disjointed thoughts, I just wanted to write them down now that we've come to one of the major turning points and I can finally write about some of this stuff without spoilers.
More than anything I'm just fascinated that so many readers had such different experiences and interpretations compared to when I read the manga blind. That in itself isn't unusual because everyone is different, but the stark contrast certainly was a newfound experience for me.
This also demonstrates why shoujo works tends to be isolated in their own bubble. This one crossing that hurdle and being placed in the spotlight among a much broader audience/demographic certainly created a more diverse pool of opinions compared the original release, whose audience was much more consistent in its reception (there was speculation there too, like the all three friends cheating theory, but it followed the story much more closely. I don't think I ever saw comments about this possibly being an intervention on the friends' part, for example). Excluding some of the misogyny I saw, I think that extra clash created a fun discussion environment.
Regardless, hope you'll stick around for the rest of the ride, there's still plenty to uncover!
