I played through most of the game, that is the entire game from the MC's perspective and bits and pieces of the MC's wife's perspective so I'll give a rundown of how the plot went.
There's 4 main characters: the MC, his wife Kairi, the fat dude next door Manzo and Manzo's wife, Yuuna. (These are the names the translator gave me so they're likely to be incorrect but for the sake of this summary I'll be referencing to them as such)
The MC and his wife have been married for a decent amount of time and have just moved into a small apartment housing that is affordable. Its a pretty decent place and their neighbours, Manzo and Yuuna are pretty decent people who are newlywed. The problem is that at night, their neighbors are fucking like animals and the walls are pretty thin so whenever the MC and his wife are trying to sleep at night, they pretty much hear all of what's going on behind the wall. To make it worse, their neighbors are pretty loud when it comes to sex and they seemingly have near infinite stamina so The MC and his wife can't really catch any shut eye. Kairi eventually brings this up with the MC and says that they have to go tell the neighbors that they can hear everything and that its affecting their sleep and after some thinking, the MC agrees to go next door with his wife to hopefully change their neighbors' ways. They do just that and Manzo and his wife are seemingly pretty embarrassed that their lovemaking has been heard for several days straight and they agree to stop causing a disturbance every nights. All seems to be fine and the MC and Kairi can finally sleep at night in peace. That is until a few days later, Kairi tells the MC that the neighbours are still banging like animals, just not at night time anymore. MC promises to go with her and talk to the neighbors again tomorrow. The next day, the MC doesn't really want to talk to the neighbors about it and he gets a bit tired at work so his boss 'invites' him to go out for a drink (he likely had no choice due to workplace pressure). After a few drinks with the boss, the MC gets a bit tipsy and his boss invites him to a soapland to relieve some stress. The MC is either too drunk or too pressured to refuse and so he goes with his boss. The boss recommends a girl and the MC enters the room only to find Yuuna, the neighbors wife. MC proceeds to bang Yuuna despite it clearly being a dumbass move but Yuuna's pretty chill and inviting throughout the entire thing. By the end, the MC had a good time but he asks her to not bring this up with his wife. Yuuna agrees with the MC but asks him for a favor in exchange, that is, in order to solve the whole neighbors having too much sex and making noise business, the MC and his wife should just have sex in the same room as them. The MC reluctantly agrees but notes that his wife will also have to agree to this arrangement but that it would be incredibly unlikely for her to do so.
Later that night, the MC returns home and as planned with his wife, they're going to go talk about the noise problem again. They go next door and bring it up to the neighbors. As Yuuna and the MC planned, Manzo brings up the idea of the couples having sex in the same room in order to reduce the disturbance and deepen their relationships. MC is shit at acting and is trying to act surprised at hearing the news, however his wife doesn't seem as shocked as he thought she would have. The very fact that Kairi didn't outright refuse the proposal is quite baffling to the MC. The MC and Kairi agree to go back home and discuss id they should go through with the arrangement or not and in the end, Kairi leaves it to the MC to decide their course of action. The MC of course says that they should do it since he's been in on the whole thing and so the next day, they tell the neighbors that they'll do it. The next night, they're all in the neighbors' bedroom which consists of two futons on the floor and some pieces of furniture here and there. With the MC attending to his wife and Manzo attending to his, they begin the foreplay. Its clearly obvious that Manzo and his wife are already going at it much harder than what the MC is doing with his wife but its pretty decent so far. Manzo then takes off his pants and unleashed his monster schlong to the surprise of the MC and Kairi. Manzo starts getting a blowjob from his wife Yuuna, and the MC replicates that with his wife but the difference is apparent. They then proceed to sex and once again, Kanabe and his wife are going at it like beasts while the MC and his wife are noticeably much more tame and the sex ends way faster on their end. After the MC runs out of stamina, he along with his wife simply watch the neighbors go at it for a while longer. Eventually the arrangement comes to an end and the MC and his wife return home, both pretty silent and surprised that it all actually happened. They agree to not dwell on it too much and go to sleep. The next day, the MC and his wife go to see the neighbors again (I don't remember why). The neighbors seem to have enjoyed what happened last night and are ready to do it again but then the MC and Kairi say that it was just supposed to be a one time thing. The neighbor somehow convinces them and they go for another round. By the end, the MC and his wife are going home but before that, Manzo proposes something new. Swapping. the MC of course says no but his wife is strangely pretty silent again and will uncharacteristically just go along with what the MC chooses. As the MC is about to leave with his wife, Manzo manages to strike a nerve with the MC by saying that he's a coward for backing out. At this point, there's two choices. The MC can choose to ignore the insult and live happily ever after with his wife, or he takes the insult to heart and accepts Manzo's challenge, that is whoever can make the other's wife cum first with foreplay will have their way. Should the MC win, everything goes back to normal and should Manzo win, they go through with the swapping. They set this arrangement for the next night and the MC mentally prepares himself. You all know how this goes by now, he gets outplayed the next night and the swapping begins. The MC bangs Yuuna meanwhile Manzo has his way with the MC's wife all in the same room. The MC cums pretty quickly then goes at it again with Yuuna meanwhile Kairi is getting banged harder than she's ever been in her life. Eventually the MC cums again and Manzo cums for the first time so the MC thinks the session is over, that is until Manzo goes for another round. The MC protests against this and says that Manzo already had a round with his wife but Manzo rightly points out that the MC went to rounds with Yuuna so he can't really call out Manzo on doing the same. Manzo proceeds to fuck Kairi for a few more minutes while the MC is already spent and eventually faints from exhaustion. After returning back home the atmosphere between the MC and his wife are pretty tense like always but especially so this time since its pretty clear that the MC has been outperformed thoroughly by Manzo in sex. They don't dwell on it though and they go to sleep.
The next day they go to the neighbors again and Manzo apologizes for the tension between them last time and reminds the MC that they're just doing this for fun and to strengthen their relationship. The MC kinda accepts the apology. A few days pass and Manzo eventually tries to push the limits again by swapping again, but this time in separate rooms for the entire night. The MC takes Yuuna to his bedroom meanwhile Manzo and Kairi have sex next door on a camera for the MC to see. The MC is spent pretty fast and ends up lying on the bed with Yuuna, watching the real time video of Kairi and Manzo. Eventually the MC tries to have another go at Yuuna but only manages a single round meanwhile Kanabe and Kairi leave the view of the camera to the displeasure of the MC. Eventually Kairi and Manzo return to the front of the camera only to resume banging all night and the MC decides to simply take a nap with Yuuna. The next morning, he wakes up and talks to Yuuna a bit, deciding to go see his wife next door soon. He then hears more moaning from next door which means that Manzo and Kairi are likely still going at it. The MC notes that is against the rules since the arrangement was for the night only so he rushes over to next door in order to chastise Manzo. Manzo opens the door and Kairi is there too, everything seemingly normal. Manzo and Kairi both deny having sex in the morning and blame the television instead. The MC doesn't buy it but he lets it slide. Over the course of a few days the swapping gets increasingly kinkier. They decide to swap wives for an entire date and the MC has a good time with Yuuna at a restaurant and love hotel and then returns home. His wife is late and past curfew though. Her excuse was that she overslept after drinking a bit too much but she does describe the sex she had with Manzo at a love hotel as well. The next swapping sessions, for breaking the curfew Manzo makes it up to MC by inviting him and his wife to a swapping date at an expensive hotel. The MC takes this apology and goes the next day. Manzo and Kairi go on their own date in the hotel meanwhile the MC and Yuuna chill by the pool. The MC gets a choice to either go look for his wife and Manzo or spend some sexy time with Yuuna. This choice sets a major branch for the story.
Should the MC look for his wife instead of staying with Yuuna, he'll end up searching around the hotel but end up with nothing since he can't find Kairi or Manzo. He notes how he should've just spent some time with Yuuna. Eventually the date is over and they meet up by the pool. If the MC did stay with Yuuna he just has some sex near the pool. Manzo and Kairi eventually return and the MC notes that they have an afterglow of sex despite their claims that they just ate some dinner at a restaurant. They go home and all is well. The next night they swap again but this time they swap their lives as a couple. So the MC and Yuuna live in MC's house for the entire day meanwhile Kairi lives with Manzo for the entire day. The MC and Yuuna have a pretty normal couple life for the most part with some sex in between meanwhile for the entire day, its nonstop moaning and panting from next door. By this point the MC has long since realized that Manzo has him utterly destroyed in the sex department but he still persists with the current state of affairs. Yuuna on the other hand milks the shit out of the MC for the nights until nothing is left in his balls. All in all a good day. The MC wakes up the next day beside Yuuna and to no one's surprise, Manzo and Kairi are still going at it. Eventually the MC goes back to pick up his wife and all is well. The MC then goes to work and on his way back he runs into Yuuna. Yuuna mentions that Manzo has no job and all of the money in their household comes from Yuuna's prostitution. The MC notes that is pretty fucked up and that he's worried that he's being caught up in Manzo's pace and that Manzo is potentially toxic for his relationship with his wife. Later that night the couples meet up again and this time, Manzo makes a giant leap and suggests they swap lives as couples for an entire week. The MC's wife once again uncharacteristically leaves the decision making to the MC, something which has sadly become too common by this point.
It is at this point that the choice you made decides where the story progresses. If the MC chose to look for Manzo and Kair back at the pool then he'll refuse Manzo's suggestions and cancel the swapping arrangement. Life goes back to normal and the MC just goes to work everyday and meets his wife after work. After a while though, the MC notices that his wife has been acting strange. One night he returns home and finds that his wife has a pube on her mouth, likely from a messy blowjob with Manzo. In full alert mode, the MC immediately bugs the house and the next day his worries prove true. Kairi's been cheating on him with Manzo. By this point the MC is pissed but firstly, he wants to ascertain it with his eyes. He lies to his wife that he's gone to work but instead stays behind and waits for his wife to go cheat on him. She does exactly that and the MC enters the Manzo's door, walks in to the bedroom and finds his wife Kairi taking it up the ass from Manzo and clearly enjoying the hell out of it. Kairi notices that the MC is watching and tells him its not what it looks like, only to immediately cum from Manzo's dick. MC rightfully questions what is going on but first beats the absolute shit out of Manzo and leaves him lying on his bedroom floor. The MC takes his wife back to their home and immediately questions her with full aggression. Kairi is clearly distraught and tries to explain herself but the MC's nonstop aggression leaves her with very little room to explain herself. Eventually, to get the MC to shut up Kairi shouts back at him and tells him that he simply can't satisfy her anymore in a taunting attitude. The talks about sex with Manzo and that the MC with his tiny premature ejaculating dick just can't do it for her anymore and that she was the one to go to Manzo after the MC called off the swapping because she was starting to become pent up. She also brings up that the MC seemingly has a better time with Yuuna than he does with her. After taking all that in the MC is pretty damn surprised and is wondering if this is the end of their relationship. The MC also notices that his wife is acting like she's still hiding something. At this point there's two options. The MC divorces his wife on the spot and goes to live in a new house by himself only to eventually run into his Kairi, now his ex-wife, several years later and she clearly has a daughter. The other option has the MC call out his wife and tell her that she's still hiding something from him. He tells her that no matter what she's hiding from him, he will unconditionally love her and that all he wants it the truth. Kairi breaks and tells him that Manzo has dirt on her and the MC. If she chooses to disobey him, Manzo has pictures and videos from various swapping sessions and cheating that he can use to ruin their lives and make the MC and his wife lose their jobs. The MC fully forgives his wife and swears to her that he'll solve this tomorrow. Tomorrow comes and the MC confronts Manzo in the latter's house. The MC sees Manzo, who's face has been fucked up royally from the MC's ass whooping and tells him that he knows he's blackmailing Kairi. Manzo spills the beans on everything and says that all he really wants is to turn the MC's wife into his personal meat toilet. He says that the MC can't do shit because by the time the MC goes to the police, the videos and pictures will already be uploaded and their lives forever ruined. Furthermore, the police might believe Manzo over the MC since Manzo is the one who's injured to the point of looking like he got hit by a car. MC then reveals that the phone in his pocket was connected to the police phones and that the police is already here. The MC proceeds to hold Manzo down and prevent him from uploading anything until the police arrives. Manzo yells at Yuuna to help him but by this point, Yuuna has likely had enough of his bullshit. In the end, the day is saved, the MC stays with his ife, Manzo goes to jail so that he may learn the pleasures of anal sex from the opposite perspective and Yuuna is left alone and divorced, though the MC says that he'll take her in and she can live with them later. Unfortunately however, Kairi is pregnant and its not the MC's kid. He asks Kairi what she wants and she says she still wants to have the baby to which the MC agrees with her decisions. A couple months later, Kairi's stomach had grown quite a lot but now she's in a loving relationship with the MC. Their sex life has been renewed and now they're truthful to their feelings and desires. In their sex scene, the MC repeatedly asks how he stacks up to Manzo to which Kairi says he's better than Manzo. The MC asks for the truth to which she says that Manzo was ways better and she completely describes the sex they had while MC is pounding her. The MC feels jealous but he feels a new vigor in him and continues to bang Kairi who this time says that the MC feels good. He's still not better than Manzo but he doesn't have to be and he and his wife are now completely honest so the sex is better than ever. Lastly, the MC tells her that he will try his best to love the child even though it isn't is and that if he is unable to properly love the child, Kairi has the full right to divorce him. The End.
The other route goes back to when Manzo proposed to swap couple lives for one entire week. In this one, the MC agrees with the proposal despite full awareness this might not end well. Three days later the swapping commences. The MC says goodbye to Kairi and starts his week with Yuuna. Its pretty normal at first and the MC is enjoying the experience. From the moment Kairi went next door all the way til night time, she's been banging Manzo and the noises rarely ever end. On the other hand, the MC comes back from work and is ready to bang Yuuna at night but Yuuna tells the MC that she has to go to her job at the soaplands so the MC will be alone for the nights. The MC decides to stay in his room and take a nap but the nonstop noises from next door tempts him to jack off to their sex. Eventually when Yuuna does return, she has sex with him a bit before they go to sleep. The next day is pretty similar except the MC has Yuuna for the entire day and occasionally has sex with her. The following days are pretty similar after that, Either the MC has Yuuna all to himself or Yuuna does her job at night. The most consistent thing is that for the entire week, Manzo and Kairi are having sex with very little breaks outside of Kairi's part time job. Over the course of the week, the MC starts opening up to jacking off to the noises he hears next door while he's alone and unknown to him, he might be developing a bit of a NTR fetish. All good things must come to an end though and so the swap comes to a close. The MC goes next door but no one is answering it. The MC can hear the moans so he knows that they're still banging so they most likely just can't hear him. He opens the door halfway and manages to peek at his wife getting banged. She sees him to but it its pretty clear that she's still enjoying sex with Manzo. Manzo says that he'll give her back after he's come and he's done just that. He cums into Kairi raw right in front of the MC for the first time. The MC is surprised and angry since he didn't know Manzo was tapping his wife with no rubber for the entire week but he reigns in his anger and does acknowledge that he was doing the same to Yuuna as well. He goes back to the house with Kairi and talks to her about it and tells her that he's not angry at her, he just wants her to tell him these things before she does them. All is well and they go to sleep. The next day, the MC is coming back from work and stumbles across Manzo in front of their apartment. Manzo talks to the MC and suggests a new play. He wants the MC to lend him Kairi whenever he pleases and the MC can do that with Yuuna. All they need to do is inform the other by phone before it happens. Manzo tries to spin this to make it sound like a good idea for the MC but he sees past the bullshit and realizes that its pretty much just a win for Manzo since Manzo will be doing way more borrowing than the MC.
At this point the MC has two decisions, either do it or not. If the MC chooses to not do it, he'll immediately go to his wife and tell her that they're getting the fuck out of the apartment complex because Manzo is up to some shady shit. Kairi agrees and they move out and continue they're loving relationship. If the MC does go through with this lending then Manzo is pleased and the MC realizes that he actually wants to see Kairi get fucked by Manzo. He goes to his house and sees Kairi but is unable to tell her about the deal he made with Manzo without her permission. He decides to do it the next night and goes to sleep. The next day while the MC is at work, he gets a message from Manzo that he's going to borrow Kairi now and the MC reluctantly allows it but notices that he hasn't told Kairi about the arrangement yet. That means that if Kairi does actually bang Manzo that night, she will be knowingly cheating on the MC. When the MC reaches home and looks through Manzo's window he sees Manzo banging the senses out of his wife. At this point the MC has his confirmation that his wife would cheat on him with Manzo given the chance. As he peeks at the scene he starts to masturbate to it, clearly beoming addicted to NTR. Yuuna walks past and notices what's going on so she offers to blow the MC while he watches Kairi's cheating. Throughout the scene Kairi admits that the MC's dick is tiny and cums to fast and that it will never match up to Manzo's. The MC is hurt but also aroused and Yuuna even says how she agrees with Kairi, only adding some more fuel to the fire. The MC says he's seen enough and goes back to his house and Yuuna asks to join him to which he agrees. With the MC and Yuuna in his bedroom and the moans from next door being louder than ever, the MC asks to bang Yuuna, but she refuses. Since the MC hasn't asked Manzo to borrow her, she can't bang the MC because that would be cheating, like his wife. She does however agree to sleep beside him. After that, the MC never confronts his wife about the deal he made with Manzo and always allows Manzo to bang his wife. Kairi is therefore cheating without knowing that the MC is in on the whole thing. A couple days later, the MC comes back home from work and like always, Kairi is cheating on him next door. He goes to sleep after jacking off by himself only to be woken up later by Kairi who'd wearing kinky lingerie and covered in sweat and other fluids. She seduces him and so the MC bangs her but notices how it seems she's faking enjoyment and how she's been stretched out by Manzo's dick so he likely can never satisfy her ever again. After banging her he goes back to sleep. A couple days later, Kairi tells the MC that she's pregnant with his child. The MC is puzzled because he only had sex with her once meanwhile she's been banging Manzo everyday for several weeks now. The MC asks her if she's sure to which she says yes because when she had sex with Manzo during the week swap, she was on the pill. The MC of course knows that she's kept on seeing him after the week swap and he sees a look in her eyes. By now he's realized that she's lying to him and that his wife pretty much just has Manzo's dick on her mind at all times. He's both horrified and aroused by what his wife has become and he accepts her lie. Cut to a few months later and he's pretty much been NTR'd completely at this point but he still lives with his wife and is feigning ignorance to her cheating. Whenever his wife goes to cheat with Manzo he calls over Yuuna to bang her. The game ends with the MC and Yuuna banging while hearing Kairi next door being made into Manzo's personal bitch, all while Yuuna tells the MC how much better Manzo is at sex than him. The End
And that's all the routes from the MC's perspective. I've only seen some parts of the Kairi's perspective but I'll talk about the important ones. At the start of the game, after the MC and Kairi consult Manzo and Yuuna about the noises, Kairi was actually masturbating to the noises they were making in the morning and afternoon. Eventually she gets caught masturbating to them and even ends up giving Manzo a cleaning blowjob, presumably because of blackmail. That's also why whenever Manzo introduced an even kinkier swapping play, she'd always stay silent and accepting to the MC's surprise.
For the divorce ending, she stays with Manzo and is pregnant with his baby and is either constantly banging him or being whored off life Yuuna at the soaplands. She's eventually thrown away by him after he gets bored of her and so she lives life as a single mother of Manzo's baby.
The ending where Manzo gets arrested is pretty much the same.
For the ending where the MC refuses to lend Kairi and goes to live with his her in a new house, its revealed that she's still seeing Manzo behind the MC's back because Manzo still has blackmail material on her so she can't escape.
For the ending where the MC develops his NTR fetish, its revealed that Kairi was actually spying on the conversation between the MC and Manzo the entire time and so she knew that she was being lent to Manzo. So the MC thought she was knowingly cheating meanwhile Kairi was actually just going along with the MC's fetish.The catcher is that she misread the MC's intentions. When she heard the MC talking to Manzo, she expected him to come and tell her. When the MC didn't tell her about the deal she started to believe that he didn't trust her and slowly stopped caring for her and started favoring Yuuna instead. So when the next day, Manzo comes to her about the lending, she thought the MC was just giving her to Manzo so he could be with Yuuna. After that the events just play out the same as from the MC's POV.
And that's it. I might have missed some details or mixed around some events but this is all from yesterday's memory and I'm not really planning to play it again anytime soon. Overall a decent NTR game but compared to the previous Kabe games it was underwhelming, especially when it came to Manzo since he's really just a piece of shit. Yuuna also gets underutilized, especially in the endings despite getting a good amount of focus and is actually built up pretty well. Welp, that's all folks.