I thought Kyouko was suss from when she was talking about her failing marriage but I thought we were going to get a misdirection where she was cheating, just not with Rei. Like a whole "All my friends have dark secrets.... just not that particular one"
I will say when they went to the roof top bar, and Haruto just HAPPENED to have slinky evening wearin his bag, I thought maybe it was maximum bait and there was going to be a surprise celebration for Mahoro. and that's why Rei had been acting weird, etc.
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.
Its less his personality and more his approach. He's doing the "Having trouble with your relationship? You should cheat on your husband with me. Haha j/k. Unless..." type behavior. As
@MrMeh &
@Birdulon point out, he is approaching a married woman who is having relationship troubles in a flirtatious way. Its scumbag behavior, and its made worse by this is clearly the author's ideal husbando (which is why in her mind it was OK for him to do with no further narrative justification).
He could have been introduced after the divorce and he probably would have been cheered.
Rei is inconsiderate, but Haruto is a douche.
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.
Rei's main flaws are being inconsiderate/self-absorbed and not a mind reader. (Also controlled by his mother.)
When Mahoro finally snaps at him and actually says what she wants and holds to her guns, Rei complies (incompetently but still). Even Kyouko calls out Mahoro for not speaking her mind.
No one is going to fault Mahoro for not wanting wanting put in the effort to fix her husband (people are going to question why she got married to the guy in the first place being this seems to be his default state and not something that appeared out of the blue) because she shouldn't have to make him a functional person but we also aren't going to demand Rei be strung up either.
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 can fix her/she can ruin me" is mostly jokin, and you act like the usual Shoujo manga doesn't start with the FMC being sexually assaulted, usually by her eventual love interest, who she spends at least a good portion of the manga fixing.
But to your point:
I don't see there would be much different. Inconsiderate self-absorbed Mahoro & selfless Rei doing all the housework would be the same. Though usually in those set ups, the guy works his white-collar slave gig and comes home while the useless wife just shops and does things like shopping/cafes/spas with her friends. And the fact "Rei is sort of useless at home, but brings in most of the household income" is why the useless husband characters usually gets more support. If Rei was unemployed and just playing videogames/gatchas all day, he wouldn't get any support.
But very few manga have the male "bad spouse" be a complete drain on the household.
(and yes, she works, he got her to downplay her career etc. But it doesn't change he is the primary breadwinner and so isn't COMPLETELY useless)
No one was coming to the defense of Rukia's brother in Tsumi to Batsu no Spica once the truth of him leeching off his sister to gamble and drink was out.
The only thing that wouldn't map 1-to-1 would be femHaruto. Haruto's lines from a woman to a man wouldn't map without additional actions by femHaruto just due to dating dynamics. Like just imagine younger femHaruto going to Rei, giving him bedroom eyes, a sultry grin, touching his chest and saying "If you get divorced, why don't we date?".
Even when her brother says "Stop it! She jokes around like this all the time, ignore her", everything she does will now be tainted by her being a vixen.
Everything after that, Perfect Rebound Pixie Dream-Waifu showing up out of no where with zero flaws and little personality would get the exact same reaction as Perfectly Prepared Date Detective & Hairdresser Haruto does from
guys anyone with sense.
Bad person to many of us would require actual malicious intent rather than just someone being deficient.
I still choose not to attribute intent to Rei's faults.
Rei is kind of a shit husband, but he's (so far) not a shit person.
You can (sometimes) fix a bad partner with couple's counseling, you cannot fix a shitty person*. (inb4 'lol therapy or honest self improvement in Japan? Let alone manga Japan?')
Though I will say his reasonings for rejecting her are sort of weak and more "you aren't hot enough for me to cheat with" than any commitment to his wife.
edit: Forgot about him snapping at Mahoro earlier.
*Except for my favorite toxic waifu. I could totally fix her.
It stems for me from the fact he mentioned his romantic interest in Mahoro initially.
It's really poor taste to say that to someone who's having relationship problems and thus puts a lens over all later interactions with him involved.
I dislike him for that reason, but in addition he's being set up as "Le Perfect Rebound, But No one understands him but the FMC and that's why he's still available".
Like dude even he does hair, comes prepared for a swanky date at a bar.
At the same time though, I've never actually read a manga which addresses the genuine things men find irritating in women.
The only aspect I can think of is the pecking order/bullying stuff but the love interest is always the victim and thus you don't get the POV of seeing your love interest act in such a nasty way.
If there were a manga about shit tests, insecurity projection (such as blaming them for something dreamt up overnight), passive agressivism and not actually being interested in fixing a problem, only venting, then I reckon the reactions would be similar to this manga.
Preach.
You have manga like "I got tired of childhood friend now exgirlfriend's constant abuse" but the behavior of antagonist is so ridiculously over the top it hard to take seriously.