I don't know how it compares to KZ as I was only able to read like two or three chapters before I just couldn't take it ( particularly remember one bit where she was hanging out with the MC at a festival or something when some other guys showed up and invited her to go with them, and even when he protested she agreed and left, and I honestly just couldn't take anymore). However, as far as this series goes...
No, Mako does indeed love Kouhei and love him a great deal. It sort of sets up an odd conflict where the two of them are very much in love and devoted to each other, except for the fact that for some reason that even Mako can't understand she simply doesn't feel much if anything when he touches her. No amount of kissing, foreplay or sex seems to even give her a tingle. She adores him, but for some reason her body just won't respond in bed. So, at the start of the story, she asks him to try "swapping". He hates it, but does it for her. They really only have a handful of "swaps". First with a husband and wife, which is nothing but traumatic for Kouhei. Then they do it a couple times with a guy named Hikaru and his girlfriend Hina who's just as much opposed to the whole thing as Kouhei. After a couple meets with that couple, Mako is surprised to find that she's becoming extremely jealous seeing Kouhei and Hina together. She talks to the married couple about it and about her problem, which implies that Kouhei is a little too much of an "herbivore", prone to not really standing up and saying what he wants and asserting his will. They suggest some stupid "rating" system where she'd rate every step from "felt awesome" to "felt nothing", and ends up with just a bunch of "nothing" down the line. Despite this, she never sleeps with anyone else again. After that first time she felt jealous she apparently decided that she didn't want to be with anyone else or make him feel those feelings. Eventually Kouhei does have a temporary affair with a classmate named Iroha, which he feels very guilty about but aren't against the "rules" that Mako herself has said are still in play (though she also confirms that she's been 100% faithful since the trip). That said, Iroha has no problem responding to his every kiss, his every caress. At the current point, Mako's career is in jeopardy due to someone having spread rumors about her (which she can't entirely refute since while she doesn't know the details she knows they can't be too far from the truth), and next (final) chapter they'll be meeting with Mako's mother.
It's definitely a bit different from KZ on a lot of points. For one thing, as far as I was able to tolerate KZ the male and female leads weren't actually an item, it was just a guy who likes a girl who seems to be cool having sex with anyone anytime, even if she was hanging out with him at the time. Here, it's a couple who have been dating for a long time and have both at various points talked about marriage. Additionally, while KZ has the girl doing other guys all the time throughout the story (far as I know) without remorse, this one has the girl sleep with two men besides her boyfriend specifically because she thinks it'll help their relationship, only once or twice with the first and maybe two to four times with the second before she realizes that the whole thing is only making things worse and causing them both pain, so she stops. Instead of being about a guy who's in love with a girl who won't stop sleeping around, it's more a story of a guy and girl struggling to deal with a situation where their sexual relationship is failing to fulfill the way their romantic relationship does, and how much pain can come from this sort of thing.
Ok. Seems like something i could get into then. I do like the drama, and i was able to find the first 10 or so chapters somewhere, where they kind of meet Hikaru and Hina and and Hina and Kouhei go out instead of doing it in the room, and I liked it well enough, Hina acted as a 'pressure release valve' after how fast paced and eroticism forward all the other chapters felt
particularly remember one bit where she was hanging out with the MC at a festival or something when some other guys showed up and invited her to go with them, and even when he protested she agreed and left, and I honestly just couldn't take anymore
In the doujinshi this scene is much more dramatic, and i think the Manga relies a bit on you having read the doujinshi - but in the Manga, Iida and the Senpai don't actually go have sex (yet, at least, it's a later development), it's kind of a joke that relies on knowing the other version, but serves partially as characterization that further solidifies Iida as a passive observer in her own life, which is the flaw of both the MC and her have, and kind of have to get through.
No, Mako does indeed love Kouhei and love him a great deal.
Since i've now only read the first 10 chapters, i understand she says it a lot, but since i haven't made it to a point where it really seems like it, but In that way, she is like Iida, and somewhat interesting. I suppose she is very apologetic about essentially entangling him in her fetish, which is pretty good, but, you know how it goes sometimes. it's hard to tell when so many chapters are more dedicated to swapping and his thoughts than on them together or her thoughts.
It seems like these first 10 chapters are designed pretty strongly towards frustrating the reader, since the Married couple are very aggressive and the competing expectations make Kouhei essentially a victim of a set up he was reluctant to agree to, but also Hikaru is very obviously an asshole.
KZ has the girl doing other guys all the time throughout the story (far as I know) without remorse
This is true in the pornographic doujinshi version of KZ, in the 50 chapter manga KZ with the same artist as this, she really only ends up sleeping with 3 people in total, including the MC, so similar, i think.
Iida has a fraught relationship with herself and her parents, which essentially makes her a doormat, she will 'go with the flow' to her own detriment for most of the manga.
Despite this, she never sleeps with anyone else again
situation where their sexual relationship is failing to fulfill the way their romantic relationship does, and how much pain can come from this sort of thing.
So she is a lot like Iida - since by the end of KZ, the MC and Iida have a almost comical set up that mirrors the doujinshi, but is still, in a way, a committed relationship.
I will try and find more to read up to the current chapter, so i can learn about the whys and hows, because i do like relationship drama, and messy bullshit like this.
And Hina is cute. so. I'll try to look around for translated chapters, or if you have a place or process, don't mind sharing.
