Koushiki Furin

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I think Chinami has plenty of warmth as she genuinely loves Fumiya and loves cooking for him. They are a "family" but Fumiya doesn't touch her so she keeps fucking Takahiro specially since she knows that her husband loves Naruse and keeps seeing her. That has to hurt.

I can guarantee that if for a man is quite destructive knowing that another guy makes his wife cum harder for a woman is even more destructive knowing that the dick that doesn't get hard for her, has no issues with another woman.

Takahiro keeps seeing Chinami because without that, he has nothing. As for Naruse's second kid, the story HEAVILY implies that he is Fumiya's son.

The author in a few pages just guaranteed audience for his next work.

This makes absolutely no sense to me. 🙄😮‍💨 Hey folks, does this make any sense to you?
 
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As far as the ending of the main story goes, aren’t four of them enjoying the cheating?
Like, it might wreck her a bit more seeing Fumiya and Naruse is also cheating, but she’s also enjoying her own secret relationship.

For the children, it’s kind of expected :D

Was hoping there’s at least something from Takahiro’s side.
Well, maybe it’s because how they got into that relationship became how they go through with it. But 10 years for sexual only relationship is really lasting without them getting bored.
The author did not attach any importance to this Takahiro character at all. So he's never drawn his face. He's just a sexual instrument for this story - just furniture. The main characters are only Fumiya, Naruse and Chinami.

BTW, the author said on his X @nikumarusuisann that he's going to write a new story of Chinami about her "pure love" without erotic scene. It may be the story before Koushiki Furin and may tell the readers why she loves Fumiya so much though he can't have sex with her for 7 years after marriage. (He just could have sex with her after the project because he wanted to forget Naruse but as you know, after they had a son, he became impotent again.)
 
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Looking at the Italian scan... Chinami is quite broken isn’t she.
It’s like she’s doing the sex while “feeling guilty” as if a kind of masochist self-flagellation.

Fumiya is doing well maintaining both life though.

BTW, the author said on his X @nikumarusuisann that he's going to write a new story of Chinami about her "pure love" without erotic scene.
Is it the Twitter space? The archive is almost 3 hours, and I really can’t stay to listen to stay that long whoever is speaking (not even vtuber stamina singing stream).
 
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Is it the Twitter space? The archive is almost 3 hours, and I really can’t stay to listen to stay that long whoever is speaking (not even vtuber stamina singing stream).
I’m not sure, but it will likely be published in Weekly Young Magazine, the same magazine that previously serialized Koushiki Furin. So that the existing fanbase can read this prequel. It may be a romance series recounting how Chinami met and fell in love with Fumiya.
 
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I’m not sure, but it will likely be published in Weekly Young Magazine, the same magazine that previously serialized Koushiki Furin. So that the existing fanbase can read this prequel. It may be a romance series recounting how Chinami met and fell in love with Fumiya.
Prequel? Yikes! 😨
And to think we couldn't have peace here... 😭

Nikumaru, you bastard!
 
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Wow this was a story I was following at the start of the year and I was surprised to hear it was intended as a short publication and ended before I caught up fully.

I had friends interested to also know how the story concluded so I caught up and translated the story for them (from my native language). While I am no scanlator, the best I could do was to translate the overall story into english and provide some exact quotes from major scenes, but bear with me as I wrote this in between 3 working days and you might find me swapping (no pun intended) between English prose and some exaggerated vernacular… I’ll swear alot, I apologise

Intro (Chapter 1)
Fumiya and Chinami are shown to try to have sex but no cock stand. Story introduces their backgrounds - They're married 6 years and are ages 29/30, likely sexless due to Fumiya’s impotence, and still with no children despite Chinami wanting children. Parents-in-law scolds him for this, but Chinami blames herself for being not attractive or knowledgeable about sex.

Fumiya is a Head Of Department in his company, and his colleague/friend teases him while smoking together at the rooftop with Fumiya that a new colleague joining them today was his "type". Left alone on the rooftop, he cock stands when seeing her staff pic on his phone and faps coz its been a long time since he's been this aroused. He gets caught by the new colleague, who is of course pissed off.

On the way home, Fumiya/Chinami get arrested by govt forces for a non-productive marriage (no children in 6 years) and the govt give orders that it is a national obligation to swap partners to solve the low birth rate problem, blaming fruitless marriages. They base this solution on the theory about how studies have shown people only appreciate their home country once having lived in worse-off environments. So now the government will match each of them with the most genetically incompatible humans so that they suffer in their new environment and develop a strong desire (i.e. be in heat) for their original spouse; how this works is that they're forced to tolerate semi-living with their poor-compatibility companion in the long term (they go to work normally but stay in same house). Chinami gets a threatening device around her neck that the govt tells them "if u dont follow our instructions u will face the consequences, you know what that means hehe". Fumiya and Chinami are super reluctant but have no choice but to obey to keep Chinami safe.

We follow Fumiya’s POV; he's brought to a new house - his designated partner is the new colleague (Naruse)!

Arc1: The Routine (Chapters 2-3)
Fumiya and Naruse draws strong boundaries in their relationship, especially as they are not on good terms (remember he fapped to her and got caught).

The scene skips to Chinami, who's shown sleeping naked on the same bed as whoever she was forced to stay with; she's sadly thinking of Fumiya. Her counterpart participant asks her if she is alright. She plays along living as a couple (i.e. exchanging couple greetings) with this unknown man, and her expressions are vague at best (she’s blushing but appears worried). Behind the scenes, one govt guy asks another about this govt order: who's fucking stupid idea is this and how is this supposed to increase birth rate; it doesnt make sense. The senior tells him the theory explained to these guinea pigs (all the participants) and the hypothesis they are testing was a lie; participants were actually paired with the MOST genetically compatible humans and the hypothesis they really want to test is if marriage could be an obstacle to birth rate (between compatible humans) instead.

Naruse realises over time that Fumiya treats her quite well; Fumiya notices she smiles more with him; they're slowly feeling attracted to each other over 2 months in this living condition.

Fumiya walking back home alone after work thinks about Naruse (wtf) and his wife (Chinami); he resolves himself to stay loyal and a govt officials appears and tell him that today, he can go back to his own wife. Naruse is notified and is surprised that she felt disappointed that Fumiya would not be eating her dinner tonight.

Fumiya returns to Chinami’s own new home. Chinami is depicted to have become alot more "sensual" (kudos to the artist, I think this was masterful) even though overall appearance hardly changed.
Chinami tells Fumiya, we can prove to the govt the experiment no need continue and was a success by having successful sex; she states will try her best. She notes Fumiya is quite shy about showing off his dick, Fumiya explains its coz he hasn't had sex in very long time (revealing to her he didn't sleep with Naruse). Chinami is slightly startled, but they go at it. Mother fucking Fumiya cock stands but when inserting he suddenly thinks about Naruse and is turned off. Chinami is clearly very sad, and says that she will make sure she is more "womanly" next time. Mother fucking Fumiya just thinks “how come my wife more pretty now, and why I only think of Naruse”, and returns to the Naruse’s home.

Arc2: The Experiment (Chapters 4-5)
Fumiya comes back to Naruse’s house and she’s appears in heat for him and ambush-kisses him. He reminds her he has a wife, but then the govt messages him say “bro we need to test kissing to see if it can reawaken your desires; AND submit video evidence, or else your partner's life is at stake”. He tells Naruse "oh u just now approach me to do this test?"; Naruse is confused but says yes anyway. Fumiya says ok leggo try kiss we are all doing this for our beloved.

They kiss and Fumiya realises they need to end the kisses soon before he catches feelings for Naruse. Naruse confesses her ambush-kiss wasnt for the experiment, but because she also returned to her husband but had unhappy sex with him: she could only think of Fumiya and would not reject going physical with Fumiya.

At this point it is revealed that the houses all these couples live in are under constant surveillance and the couples are being monitored for their relationship progress; the Gov officials behind the camera says "finally! this pairing's so fucking slow" (suggesting others like Chinami, could've progressed further already). They noted the reluctance of the Fumiya to cross boundaries, saying "we can always resort to that...."

Naruse pounces on Fumiya, they dry hump until both orgasms. They proceed to sex, but during attempted insertion this MOFO Fumiya NOW thinks about his wife (guy is probably allergic to insertion). He rebuffs Naruse; the gov officials secretly watching are like "fuck this guy, ok this pairing has failed, lets go with "that" ".

The next day, Fumiya sends Naruse a long apology sms about how they shouldn't succumb to temptation even though he admits Naruse is a pretty girl. He returns after work to Naruse’s home as usual, but hears sex sounds of a woman shouting Naruse's husband name (introduce Takahiro). He is paralyzed at the fear that the voice is Naruse’s being banged by her own husband.

Fumiya overcomes his thoughts to go and "save" Naruse or at least intervene. He finds her crying on the floor heartbroken; govt officials had sent her a DVD of Takahiro fucking an unknown female (see my section on hints). Fumiya rushes in to hug and console her; telling her she doesn't need to explain or say anything. They kiss. (author inserts a full page of a photo of Fumiya and Chinami happy together...)

Fumiya and Naruse are then shown going through foreplay; Fumiya is like wtf my dick damn big for the first time. They contemplate making love while in embrace; Naruse says yes but she requests that Fumiya first needs to call her by her first name. They call each other by name. They move to be in a missionary position… then got cockblocked coz police came to rescue them.

Arc3: Time skip (Chapter 7-8)
4 years have passed. The experiment was explained by Fumiya to have been done by a govt official gone rogue. Fumiya says life is peaceful now; the author describes that it is as if the experiment had not happened.

Fumiya now has a son and is living with Chinami. Chinami returns to looking "normal" and had made new friends at the son’s childcare. Fumiya explains more about this he had quit his high post job and moved to a new home to completely avoid Naruse. He admits that everyone, including the police, is sworn to secrecy about the experiment. (Unfortunately IMO) Fumiya says he didn't discuss much with Chinami about the whole hostage/experiment situation either, as they think that bringing up the topic would be a point of no return. He was fiercely rebuked by his own parents (who cut ties coz he gave up his career) but is comforted that his wife fully supports him. They move to a new home with government assistance. But he admits one thing; he could not just suddenly move on mentally. In order to erase Naruse’s face from his mind, he had been having mad sex with Chinami every night immediately after they had been saved from the experiment.

Now past four years, Fumiya in his office wonders why his erectile dysfunction is back, but says it doesnt matter as he already had established his family (he has his kid) and new work. Fumiya avoids the nomikai at his new job to bring back desserts for Chinami and her new friend, this new friend also brought her own daughter - her new friend is mother fucking Naruse

Fumiya and Naruse reflexively call each other by name, but then quickly return to formal pleasantries; Chinami luckily doesnt catch that. The adults talk about how both their kids get so along and are inseparable, and Naruse says she envies how good the relationship is between Fumiya and Chinami.

Fumiya fetches Naruse home by car along with the whole family. Chinami asks him to stop at a crossroad when their son needs the loo; Fumiya wonders why Chinami knows about a convenience store here. Left in the car with Naruse, Fumiya thanks Naruse for befriending Chinami in this new environment, and hopes they continue to get along. Naruse holds his hand, asking him if that is all he wants (i.e. what about him getting along with her too).

Naruse asks why he disappeared and cut off all communication with her, and admitted she was willing to do whatever she could to stay with him. She had tried to forget about him to get back to her life before the experiment, but could not. Fumiya drops a bomb to the readers: Fumiya says that he did so because he could not live with Naruse close by his side, as he would have to live everyday pretending to love someone else (his wife). They kiss in the car.
 
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Arc4: Adultery (Chapter 9)
Months have passed; the children are growing older. Fumiya reveals that after that kiss, he and Naruse continues a platonic relationship (he is fucking delusional; they hold hands whenever Chinami is not looking).

At Fumiya’s workplace, his attitude and performance has improved. A male junior colleague ask what's his secret, if there is one. Fumiya ponders and replies there probably is! Later, Fumiya refuses the nomikai as usual and leaves office. Back in the office, the male junior suggested the secret is probably a woman. Another colleague rebuffs this suggestion, saying that Fumiya isnt like him. They acknowledge that Fumiya is a family man (cos he avoids going parties or drinks after work). The next frame reveals Fumiya parking his car, and the woman waiting for him is not Chinami; its Naruse…

They kiss and cuddle in the car, Fumiya happily sharing about his day at work and how he's called a happier man now. Naruse asks "are you not happy?" Fumiya happily acknowledges that his colleagues hit it on the nail. Naruse wonders about fate poetically; how is it that two genetically incompatible people, ends up meeting only because of this incompatibility, and now hungers for each others' connection? She ponders out loud "so what if its supposedly wrong?" (i.e. for incompatibles to be together) Fumiya acknowledges this and replies that even god makes mistakes. Naruse expresses that she is in a state of happiness as they embrace and moan as the camera pans out.

Later, Fumiya drops her off somewhere. He admits that they keep cuddling and kiss, promising that beyond kissing is a path of no return. Fumiya receives a call in the car; the police have completed investigation of the experiment and would like to explain their findings to Fumiya if given his consent. He says yes, and the police reveals the truth the readers have already known: the experiment was not about Least Compatible couples, but pairing the Most Compatible couples.

Arc5: Point of No Return (Chapter 10)
All four characters meet at school (author makes a point to always invasively crop Takahiro somehow; either his face or body) for their children's school performance. This time, Fumiya and Naruse did not acknowledge or hold hands when they stood by each other.

Fumiya and Chinami are volunteering to videotape the performance; they stand at the back of the crowded auditorium with a tripod and camera. He tells the Chinami to go to the front row (she has a handheld camcorder) as their kids are coming on stage soon; he will take up the recording duty of the show from the back of the crowd. Alone, Fumiya admits that he and Naruse did not meet ever since the police call, reasoning that the compatibility reveal more than convinced him that continuing to meet Naruse would inevitably destroy both families.

Fumiya feels a brush on his hand; Naruse with an angry appearance, is suddenly beside him, asking him why he had broken contact with her. Fumiya struggles to reply. Naruse tells him that she knows; she knows that they are the PERFECT genetic couple (probably received the same police call). Fumiya acknowledges, telling her his reasoning that they would "inevitably..." Naruse cuts him off with a change in expression; looking sickeningly happy and excited, she tells Fumiya "But I already made my choice".

(Titular device and author gospel incoming)

Fumiya is stunned. Naruse says "If we can't maintain this status quo, then we might as well take the step forward. It can't be helped after all. We are like X any Y; arranged side by side beyond our will. Since we have already been put into a formula that they (a higher being) have set, how can we normal humans reject our instincts? Fumiya, are you willing to cheat with me your whole life?"

The scene cuts away to the stage, the audience, with panels detailing the announcements and bustle of the auditorium. Chinami is clapping her hands at the end of the performance, satisfied with the video she took of her child's performance. She happily tells herself that the next target to capture in the camera is Fumiya. She turns to the back of the hall, shocked to find him missing.

This chapter closes with a full-page panel of Naruse; she's bent over a desk looking backwards at the reader, her lower torso beautifully bare. There are two hands holding on to her hips, as she pants and sweats.

Arc6: SNAFU (Chapter 11)
This chapter opens with a recap of the sounds heard throughout the school back to when Chinami is clapping along with the children' s performance. The views pans across the school, with heavy rain hitting the windows, then towards a classroom upstairs in an adjacent school building, then to a window looking over the school in which Naruse is bent over an adjacent desk. Again fully bare below, attached at the hip with Fumiya (its doggy). Their moans and words are drowned out by the music from the auditorium below, while Naruse invites Fumiya to continue making love. After a bout of sex, Naruse remarks to Fumiya "This time, we have really begun, from that very time..."

The next scene shows their "escape plan" to return to the audience unnoticed. Naruse sulks, saying that the moment they leave this room, they would return to become Child1's dad and Child2's mom. The author stealthily moves them from place to place with each panel and exchange of words. They share a moment of sadness, then offer their pleasant goodbyes saying "Please take care of me going forward, ChildX's parent". They moved out of the classrooms and are at an open stairwell moving towards the ground floor to the rest of the school. They smile sheepishly at each other one last time, then embrace and kiss

The view pans just to the ground floor; someone remains motionless under an umbrella. Chinami stares at the couple above in a mind-broken state, her eyes completely clouded and bearing a reflection of the couples' kiss.
 
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Arc7: Everyone's The Asshole (Chapter 12)
Fumiya opens the finale. He silently narrates to the reader; time flies and years have passed (based on chapter 12.5, at least 11 years as their toddler children are highschoolers now). Our capable Fumiya has been promoted again to a managerial position. He is invited to the front at his company to give his speech.

Fumiya recounts in his mind what has happened so far: He is a newly appointed manager, his child has fallen in love, Chinami has also found a job at a bookstore? (Fumiya legit wasnt sure) He has reconciled with his in-laws. He now has darker circles under his eyes, and more white hair. “Thats pretty much it” he says, “everything is smooth”.

Fumiya spots his younger colleague (the one who earlier said a woman changed Fumiya to be happier) amongst the crowd with a sullen face. He brings him to the rooftop with come beers for a heart to heart. His younger colleague explains that he couldnt get erect with his girlfriend and got into a fight. Fumiya accidentally suggests to him that he should try sleeping with another woman. Both of them are shocked.

The colleague breaks the awkward silence and Fumiya replies he was just joking. Fumiya says the colleague is thinking too much about his affliction; Fumiya explains he had experienced ED before and that Men inevitably face problems in life. Colleague is relieved to hear that it is perhaps a common problem. Left alone, Fumiya questions how he could have been so careless.

Naruse suddenly appears (this woman is pretty much a ninja at this point) beside him, asking him if he is ok and why he did not tell his colleague that part of the possible solution is fapping to a girl's photo on the rooftop while shouting her name (thats how they met). She reveals she had eavesdropped on the whole conversation, and Fumiya quips that she has a bad personality. Laughing, Naruse jokingly says she's hurt by the remark, then points out that Fumiya however, from head to toe had become a bad person.

Naruse explains; Fumiya is having an affair even though he is a dad, and the reason she's (Naruse) here is that Fumiya had used his position in the company to grant her a job at the company to facilitate their trysts. Fumiya embraces Naruse, then goes poetic (author’s gospel again): he claims that it is good that things turned out this way. "Meeting you made it clear in my eyes, that in this destiny, in the face of the formula written by god himself, manmade rules and common sense are too insignificant. There is thus no harm/matter in becoming "bad", as long as I am with you."

Naruse looks back lovingly at Fumiya, saying "I love you. For the days that come, please make sure to cheat with only me."

Epilogue: Everyone's The Asshole (Chapter 12's last few pages)
The scene begins with Chinami, who's looking out the window while it is raining. She is in the embrace of another person.
The panel pans out; shes naked in bed… with Takahiro!!! (as a reminder, it seems intentional that author leaves him cropped and appears increasingly unkept with appearances over time. You NEVER see his face, EVER. It is only with this reveal that you realise this guy resembles the guy Chinami lives with in Chapter 2)

Takahiro asks why she's daydreaming into the sky; she replies the rain reminded her of the day she saw Fumiya and Naruse kissing. Takahiro asks if the sight shocked her. She ponders and acknowledges it, but also says that she was shocked to see Naruse at the daycare.

Chinami’s turn to drop the bomb on the audience: She admits she almost laughed when meeting Naruse due to the sheer ridiculousness of the situation; the whole reason why Naruse and Takahiro were in the same town as Chinami and Fumiya (and ended up going to the same daycare) was because Takahiro chose the same location for himself and Naruse to move to for the sake of Chinami. She admitted she had to be careful not to reveal herself to Naruse, but Naruse had approached Chinami first, to befriend the one (Chinami) that was cheating with her husband (Takahiro).

Chinami (gospel incoming) remarks that Takahiro is a bad man for bringing home another woman despite having a cute and gentle wife (there's some irony here as between the two, Chinami is probably the more "cute and gentle"). Takahiro replies that Chinami is the same.

(Some heartstrings pulled here) Takahiro states that Chinami had truly become a bad woman: At the start she was a completely unwilling party, crying in tears while offering her body to another man for the sake of completing the experiment. Chinami (gospel continues) remarks, "All that doesnt matter anymore, you yourself taught me that. That man-made rules are insignificant; a man and a woman put together will be devoured by instincts. Because we cannot reject the formula written by god himself for us.

The chapter ends. Chinami notably does not recover color into her eyes when with Takahiro, remaining more or less broken in this chapter. (Author clarified that at no point did Chinami ever stop loving Fumiya). It is revealed that the title of this story is a pun: Koushiki can mean “Official”; i.e. endorsed by state/authority, but can also mean “Formula”; the plot device/excuse that the characters all end up using to justify their cheating.
 
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Overall Review
While too short to deliver what the author intended (hence feeling only superficially deep as some commenters already pointed out), I'm quite fond of some stylistic choices he chose. On one hand he tries to cooks ala Higurashi, with an overall “mystery” introduced early, then a later chapter/arc being the “answer”. The results are questionable at best.
(he only has 12-12.5 as the answer chapter
The use of his paneling, storyboard and art however, are very much more appreciable.

The Mystery
Chapter 2 sets the thriller going by showing that while Fumiya holds fast to fidelity, Chinami is suggested (left naked in her experimental quarters) to be "going through the motions" about being forced to be in a sexual situation with a stranger, although it is made clear throughout the story that Chinami had never detracted from her goal of enhancing her relationship with Fumiya. So to the readers, we are left to wonder: Did she really do it (albeit having her life at stake) with another guy and left Fumiya the cuckold?

The Hints
As pointed out by many in this comments section, Nikumaru gives us some hints - albeit barely much to work with - to try figuring out if Chinami was NTR-ed from Fumiya. Some included:
  • Arc1: Chinami was taken aback when Fumiya first returned to her and revealed that he did not have sex with his assigned companion. This was probably because she had not abstained from sex like he did. She also appears more “womanly”, suggesting more experience with the opposite sex.
  • Arc1: The experimenters assess the Fumiya-Naruse pair to have developed really slow (possibly the slowest; they said “finally started”) and not reaching the objectives of their experiment. Slow is relative, which could suggest Chinami’s pairing has progressed beyond kissing already.
  • Arc2: Chinami has a somewhat similar build with the woman that Takahiro was depicted to have sex with in the DVD sent by government to push Naruse and Fumiya’s relationship (I’ll explain later how this is unlikely, tho)
  • Arc3: Chinami was familiar with the convenience store near/otw to Naruse's new house (and thus also Takahiro's house)

What's Unfortunately Motherfuckingly Vague
  • The experiment conditions are not really explained well. How they continue daily work as usual and why the story doesn't show Fumiya and Naruse at the same workplace again is not explained. How often they are given any couple/horny tasks to push the experiment are also not explained. In chapter 4, the only example was the kissing task that lasts for 10 consecutive days. While not specific, failing which puts your partner’s life at stake.
  • Artificial stakes. Continuing from the previous line, no one knows what would happen to Chinami’s neck vice/choker (explode? poison?) if they do not abide by the experiment’s instructions. Author likely avoids this to not open a can of legal worms to explain in their universe (e.g. why govt can execute people) with his limited pages. What appears to be the same device is a bracelet on Naruse’s wrist (see chapter 3 page 1 for Naruse’s bare neck; chapter 4 for her wrist) which is arguably more safe.
  • By nature of the experiment (being paired with a MOST COMPATIBLE suggests one penultimate partner), the participants should be in an “exclusive” relationship with their new partners. However, in the video sent to Naruse about Takahiro cheating, the female counterpart does not resemble Chinami much despite Chapter 12 showing that Takahiro was assigned to Chinami the whole time. While they share their long hair and a modest chest, the woman Takahiro was banging has darker hair, wears a high and slim ponytail, wears tight clothes, has no neck device (this woman's could be elsewhere like Naruse), and the male MC does not make any reference to recognizing that the moans were from Chinami (he thought they were Naruse’s), although he should if it was Chinami's voice as Fumiya and Chinami have done good foreplay before (he also shows off his skills when they reunite) and it is only him that cannot maintain erection and moan in pleasure. The difference in appearance of the mystery woman is stark as Chinami is characterized to be cute and flowery, but a modest, plainer and petite foil (think something closer to towards Waguri) to the more modern and sexy Naruse, who is tall, has stylish hair and fashionable, tight fitting clothes on her bombshell body. Chinami is almost NEVER depicted fashionable or stylish (only in chapter 10 she dresses up for her child’s stage performance), and wears her hair more open or in the anime dead mom’s hairstyle.
 
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Character breakdown and faults
I’ll preamble this by saying that nobody was an angel in this story. Everyone kinda sucked (hence my subtitle for Chapter 12). But while I think there’s alot of people throwing eggs on Chinami,
I’m actually inclined to say that in most matters, she was the true victim of the story.

Fumiya
Our POV guy kinda aint no saint. He was loyal at first, but eventually starts to succumb to temptation after recognizing his own feelings for Naruse during her sob story. But he crosses another moral boundary and starts really cheating as soon as he is given a justifiable excuse: a scientific crutch (he is the “most scientifically suitable mate by formula” for Naruse) for his infidelity. A smart guy, he rationalizes himself by saying he hasnt crossed the final boundary coz their relationship wasnt sexual. When the author goes all poetic and Naruse is revealed to share similar rationalization, Fumiya fully falls into physical cheating. To be honest, Nikumaru actually provides hints that he is over time disinterested with Chinami (was he ever interested?):
  • Arc1: Author funnily shows that Fumiya’s phone background pic is Chinami in chapter 2. When he views his phone and notices the time, the first thing he thinks about is not Chinami but Naruse. This happens in the next chapter too. This is juxtaposed by Chinami, who just the scene before is shown to have the same phone background picture and is worried for Fumiya despite just having likely being banged against her will by her counterpart (revealed by Takahiro)
  • Arc1: Fumiya is barely shown to be excited for Chinami in general (probably coz she hasnt attracted him for 6 years). As early as chapter 3 he thinks of Naruse when Chinami is trying her best to get them out of the experiment. He does not kiss Chinami, but reciprocates Naruse’s kiss in the next immediate scene.
  • Arc1: Fumiya admitted that kissing Naruse is giving him feelings for her, calling it inevitable (thats not how it works u fuck)
  • Arc2: By this arc its clear he has feelings for Naruse instead. He is afraid of her banging her own husband, and is afraid of catching stronger feelings when they kiss.
  • Arc3: He reveals he fucks Chinami to forget about Naruse. At the end of this arc he drops the truth bomb that he loves Naruse, not Chinami
  • Arc7: Mofo doesnt know Chinami’s day job. His 20-year marriage wife’s current job.

Naruse
Naruse is shown to be a spunky but highly attractive woman, but she’s like a succubus. What at the start appeared to be an upright OL, once she realised early in chapter 3-4 that she likes Fumiya more than her husband, bulldozes her way to try to get Fumiya to cheat at every opportunity. She doesn't talk much about Takahiro other than desiring Fumiya more.
Naruse and Fumiya are depicted sickeningly sweet together once they start their relationship, and they strive towards a “happy ending” when they are found to share the same justification for cheating. In all accounts this character would have been a favourite FMC in any harem romcom, but lets not kid ourselves; beneath the lovey dovey lens with Fumiya she’s basically a homewrecker. I really liked how the artist draws them together this way, you almost forget that they are actually the villains here (until the final reveal).

Takahiro
No-face guy with a decent hairstyle, and is revealed to be Chinami’s assigned partner at the end of the book. In the main story (means not counting 12.5) he has almost no personality; most of his screen time, he is generally caring and polite to Chinami. I think it was very intentional that Nikumaru purposely crops him and covers part of his body throughout the story, almost like he is not part of the main cast. Either another panel covers his torso, or Chinami’s head covers his face, or he’s inserted into the tiniest panel.

He is the last thing on everyone’s mind. Fumiya doesnt know him. Naruse doesnt love him anymore. Until the final reveal, he was nothing to Chinami.

Preliminary: I’ll reserve judgement, until I finish translating 12.5. He turns out to be more of a dick here. But maybe he is, to Chinami, just a tool and not a person, hence Nikumaru's intention of leaving him almost like a mob in this story.

Chinami
What a shame 🙁. I think Chinami remains an enigma not because she was supposed to, but because Nikumaru ran out of runtime to explore how she developed and her motivations. Many scenes of hers are juxtaposed onto Fumiya’s own behaviours (their reaction to their phone background, their conversations about being Bad Woman/Bad man, their references to the “God’s Formula”) to contrast their situations. Chinami was forced to cheat to preserve her life, and thus did not abstain from sex at all. She physically cheated against her will, but emotionally remained loyal. Fumiya initially forced himself not to physically cheat and abstained from sex, but emotionally cheated for most of the story.

I think the unfairness of her situation (she’s a victim forced along by circumstances beyond her control) compared to Fumiya’s happiness with Naruse is supposed to be the tragic ending Nikumaru wants to contrast with, but by just giving us that copout(?) few last pages in chapter 12 (for some reason she has been sleeping with Takahiro all this while) the ending takeaway suddenly doesnt feel very coherent, or at least weakens the tragedy alot.

At the end of chapter 12, Chinami is evidently in a physical relationship with Takahiro behind Naruse and Fumiya’s back, but she retains her mind-broken state ever since she found out that Naruse and Fumiya were cheating. Her pupils remain completely dark while sleeping with Takahiro. Notably, she also cries everytime she is depicted sexually with Takahiro (in all chapters, even in 12.5), which is more aligned with the tragedy angle I assume Nikumaru wanted to initially go with before running out of pages. This is also more supported by the final page, which she, in tears while having sex with Takahiro, says “we cant reject the formula written for us”.

What is not explained yet (maybe in 12.5) was what were her motivations to continue cheating with Takahiro ever since the experiment ended. I’m of some opinion (occam’s razor) that it is a mixture of having no physical fulfilment from the man she loves (and finding it from the experiment partner), and past finding out Fumiya also does not love her back, her behaviour reinforced into (based on 12.5) what appears to be an increasingly unhealthy physical relationship with Takahiro to make up for it. I need more information on what happens during the 4 years Fumiya avoided Naruse to be clearer on this, but else its all speculation. The only clue Nikumaru dangles for us is that Chinami is suggested to be familiar with a specific convenience store, which is possibly near/on the way to where Naruse and Takahiro lives, which means she could have visited him sometime, but then its also possible that during her friendship with Naruse she could have been there.


Spoilers for 12.5
I need to translate 12.5 but from what I’m seeing Nikumaru drops us another mystery/tragedy; Chinami and Naruse’s kids have fallen in love. Naruse’s kid is definitely Takahiro’s, but what about Chinami’s? Why were these kids inseparable since early childhood? Could they actually be half-siblings?
Else, both couples continue cheating into their mid-40s, and nikumaru suggests that all parties may have become content with this arrangement (but Chinami's words and tears bring much doubt to this on her part).
 
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Takeaway
As with most NTR subplots, I think most commenters' reaction to this story is pretty justified; but lets be real we weren't gonna walk away happy in most NTRs anyway. I do think this was an ok attempt to give additional layers to an spouse swapping story. Theres gonna be some suspension of disbelief needed, but I think it was sufficient for me to imagine the thoughts and emotions Nikumaru intended the reader to feel.

Nikumaru is an NTR enthusiast, thats undeniable. Thats probably why he wanted to "do the genre good" and ended up with this more verbose/"try to be deep" story. Based on his twitter posts, he's quite passionate about this work, and I do think he feels disappointed at the feedback he's getting. I think this fell into a similar trap with his previous major work; he simply did not plan out the pacing for a satisfactory ending and ends up with clear loose ends that is more distracting than the theme he wants to focus on. For a 12 chapter story, I think simply 2 more chapters to explore Chinami would have been good round-up, instead of throwing her those meagre pages in the epilogue. Perhaps that is why Nikumaru ends up continuing with 12.5 and has (?) possibly another standalone chapter.

Absolutely no way through this story do I believe Nikumaru endorses cheating and is trying to preach "Yo folks go cheat on your devoted wives to get a happier ending than her". I'm inclined to believe his intention was to explore how a cheap, convenient excuse could be abused to justify their misbehaviours (to themselves), especially noting how in both meaning of Koushiki, the agency is externalized to a higher power (government or god forced me to do this). All the characters end up cheating, and say shouganai, thats the natural course of the circumstances I'm in. But at many points in the story, they did have a choice for normalcy. They just took the easy way out. Some won, some lost.
 
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Mar 23, 2026
Messages
226
Takeaway
As with most NTR subplots, I think most commenters' reaction to this story is pretty justified; but lets be real we weren't gonna walk away happy in most NTRs anyway. I do think this was an ok attempt to give additional layers to an spouse swapping story. Theres gonna be some suspension of disbelief needed, but I think it was sufficient for me to imagine the thoughts and emotions Nikumaru intended the reader to feel.

Nikumaru is an NTR enthusiast, thats undeniable. Thats probably why he wanted to "do the genre good" and ended up with this more verbose/"try to be deep" story. Based on his twitter posts, he's quite passionate about this work, and I do think he feels disappointed at the feedback he's getting. I think this fell into a similar trap with his previous major work; he simply did not plan out the pacing for a satisfactory ending and ends up with clear loose ends that is more distracting than the theme he wants to focus on. For a 12 chapter story, I think simply 2 more chapters to explore Chinami would have been good round-up, instead of throwing her those meagre pages in the epilogue. Perhaps that is why Nikumaru ends up continuing with 12.5 and has (?) possibly another standalone chapter.

Absolutely no way through this story do I believe Nikumaru endorses cheating and is trying to preach "Yo folks go cheat on your devoted wives to get a happier ending than her". I'm inclined to believe his intention was to explore how a cheap, convenient excuse could be abused to justify their misbehaviours (to themselves), especially noting how in both meaning of Koushiki, the agency is externalized to a higher power (government or god forced me to do this). All the characters end up cheating, and say shouganai, thats the natural course of the circumstances I'm in. But at many points in the story, they did have a choice for normalcy. They just took the easy way out. Some won, some lost.
I have to give you credit for summarizing all the points, clues, slips, and flaws that this story presented. You are truly an excellent observer and a reader of good character – even I wouldn't have been able to do that. 😅😅😅


(Except for the author, he still is a scoundrel. 🤭)
 
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For piece of details from Chinami I also want to know is how she is approaching the cheating with Takahiro before she found out that Fumiya is also cheating on her.
The reveal obviously break her mind.
In the latest chapter, Chinami’s cheating is like she’s playing a tragic role: a loving wife who is forced by another man against her will; she never stop thinking of her husband. But she also seems to be quite eager. Takahiro seems to already understand and play along, like when he said he will leave, and Chinami stops him.
But we don’t know how she is involved when she still think Fumiya doesn’t know and love only her.

As for the video message. Also yes, it’s suspicious about if Nikumaru lampshades it.
The premise of the experiment is always genetic compatibility. The committee said they’re paired with the “most incompatible” while in reality it’s the “most compatible”. But it is too convenient that Fumiya’s and Takahiro’s most compatible/incompatible partner happens to be each other’s wife.

Although, there’s also matter of sacrificing the details to focus on the plot in limited time.
First part (the experiment) is obviously just to introduce and set up the character relationship. The experiment itself is simply plot device.
 
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Could they actually be half-siblings?
Is the knowledge that in manga, hair is usual a visual clue for paternity arcane knowledge only a few possess?
Just compare a panel of Fumiya and Nao side by side. Plus the "i don't know exactly why but I think of him as a little brother" but he doesn't have the same vibes from his girlfriend (Akira's sister).
 

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