The intruder from the end of the last volume has proof that Yuriko is having an affair with Sousuke: photos of the pair, including one with Yuriko's face in it. However, that is not Yuriko's face, but the intruder fails to believe her as Sousuke has been more cold towards her despite the love and affection that she showers him with. Yuriko is saved by the appearance of the love of the intruder's life, Sousuke, who explains that he isn't cheating on the intruder as the woman in the photos is actually his sister. Technically, his half-sister as he is the product of an affair his mother had with another man. He escorts her out of the house, telling her that this behaviour is out of character (as well as illegal) for her and tells the audience (and Yuriko) that her name is Miho. Sousuke apologises for his girlfriend's behaviour and Yuriko admits that she's fine (physically), so wonders if he is and he is as he has had ex-girlfriends who have done similar and worse - one has written an entire romance novel that starred themself and Sousuke as the protagonists. He heads off to fix the door (the reason for his visit) and begins to reminisce about his time in this house, specifically a time when he and Gakurouta damaged a wall after throwing a toy plane-glider into it (not intentionally) and lucked out that Gakurouta's grandmother didn't notice. He remembers how much fun he had playing with Gakurouta and further illustrates his point by explaining his backstory.
All the adults in his neighbourhood knew about the circumstances of his birth and while they were polite and kind towards him, some did it with a sense of malice and he didn't like that as while he saw his life as normal, they saw it as pitiful. In middle school, his blond hair and bright eyes gave many female fans who called him "Prince Sousuke", much to the chagrin of some his fellow male peers. He didn't mind that as they had a problem with him, not his life. The girlfriend we saw in Gakurouta's origin story was not his first in middle school as he dated a student in a higher year, but when they broke up, his entire class knew the next day. The breakup which helped Gakurouta realises his feelings for Sousuke hit him hard, but Gakurouta being there, unchanged to how he remembered him, helped him relax and get over it.
Snap back to the present, as Yuriko suggests that he takes a break, which accepts, but his still continues to reminisce but this time focusses on finding out that Gakurouta is getting married and his wife will be moving in. Shocked at that Gakurouta got married and now upset that his 'childhood' home will now become a home for a married couple, he vents to his sister expressing desire to get married. His sister shuts him down fast pointing out that he is so quick to enter romantic relationships out of a fear being lonely or more specifically out of a fear of being pitied for being alone.
It's back to the present (again) as Sousuke asks what about Gakurouta convinced Yuriko to marry him and she explains truthfully whilst avoiding the fact that she isn't romantically or sexually attracted to him. The ultimate reason is that she didn't want to go through life alone and Sousuke feels the same way, but he also loves being in love and the activities you do in love, but his relationships never last he cannot match the strength of his partner's feelings and when single, he feels uneasy and this feeling is eased when with someone who loves and cherishes him. Yuriko asks him if the feeling of being cherished and loved could be achieved through friends and family or hobbies and the like, besides there is someone who deeply loves him and there are already beside him - quite literally as Gakurouta has just entered the room. He asks what they've been talking about and Sousuke confesses love advice, while its life advice from Yuriko. Sousuke stays for dinner (at the Hanazono's request) and leaves, but Gakurouta is concerned about his girlfriend causing physical harm to Sousuke (he has been filled in about the earlier incident), but he is not worried.
Once Sousuke is out of earshot, Gakurouta confronts his wife about what he overheard she and Sousuke were talking about - specifically the'someone who deeply loves him and there are already beside him' part as she could've outed him and besides what advice can a person who has never been in love give anyway? Yuriko runs off to her room, as Gakurouta realises his mistake and tries to apologise, but she is already in her room crying, realising that she is in a fake marriage and she and him are no more than strangers. Meanwhile, Gakurouta's grandmother is staying up late looking at photos of her grandson and his wife - she is meeting them soon.

Gakurouta and Yuriko make up after some assistance from Shou who tells them that they are both in the wrong as well as that is expected for them to fight, being complete strangers to each other, but the important thing is to resolve it quickly (which they didn't as they spent 2 weeks either avoiding each other or in awkward silence) and come to a compromise. The pair are also very busy today as they have hired a professional house cleaning team to clean (and Sousuke to do gardening) and are picking up Gakurouta's grandmother (Take Hanazono) from her nursing home to take her home for New Years via a trip to the family grave. Yuriko is intimidated by Take or more rather her intensity. The young people clean the grave before praying to the spirits whose bodies reside under the grave. Yuriko apologises for only now visiting them and hopes they will allow her to stay by Gakurouta's side despite her shortcomings. Take, on the other hand, apologises for still being alive, but now that Gakurouta's married she can die peacefully - almost she still needs to see her great-grandchild. This is going to be a problem as our happy couple aren't sexually interested in each other, they don't see the point in having children and Gakurouta has volunteered as tribute to be the bearer of the bad news.
They return home and Take apologises for being a burden on the young couple, but Yuriko assures her that she isn't as after all this used to ber house. Take corrects her, revealing she married into the Hanazono family, not born of it (explains her old age -she didn't inherit a short lifespan). The young couple realises that their bedding is in separate rooms, so whilst Take greets the cleaning company, they dash to populate the designated master bedroom - Gakurouta's father's room and there they go over their cover story again. Gakurouta volunteers to deal with the hard stuff, but Yuriko wants to chip in as well as the 2 are in this together.
The couple try to maintain the illusion that they are a happy couple, but 'old' habits die hard and are nearly slip up although the illusion is kept up. During the Red-White singing contest (a New Years Eve tradition on Japanese Tv) Take mentions talking to Yuriko's mother about grandchildren, which prompts Gakurouta to tell her the truth. Take doesn't take it well, as she believes that they are robbing both her and themselves of one life's greatest treasures - children. Leaving Take alone, the 2 reflect on what went down and to make up for not providing offspring, they promise to frequently visit her. A nearby clock strikes midnight.

The pair wish each other a happy new year. The next morning, Take acts like nothing happened and offers them some spiced sake, as it is tradition in Japanese culture for the oldest member of the family to offer it to the younger members. Gakurouta refuses the sake, on the principle that he will be driving as he and Yuriko are going to spend New Years Day with Yuriko's parents.
They arrive and Yuriko is dragged into the kitchen to help her mother with preparing food, while Gakurouta is dragged away to drink alcohol. Gakurouta passes out (he can't handle alcohol) and now that she is no longer busy, Yuriko's mother starts asking about the wedding ceremony, as she considers what the couple did (some photos of them in traditional wedding outfits) to be unsatisfactory. This inevitably leads into to a point about children, so Yuriko sets the record straight, which goes as well as last time. Her parents don't understand, as all they want is Yuriko to be happy and all she needs to be happy is to be with Gakurouta in the most non-romantic and non-sexual way possible, so all she wants from them is to respect her decision.
The next morning, Gakurouta wakes from alcohol-induced nap and instructed distantly by his mother-in-law to call his wife down, who is huffing some BL that she had left at her home. The rest of the Sonoda family arrive and all congratulate Yuriko on tying the knot and celebrate with drinking of alcohol, so the couple finally leave on January 3rd. Whilst waiting for Yuriko to be ready (she is putting on a Kimono given to her by Take with the help of her mother), Yuriko's dad talks about what Yuriko told them on January 1st whilst Gakurouta was passed out drunk. Her father thinks that she isn't thinking long term and is too spoiled and Gakurouta acknowledges his opinion, but he stands by his wife's decision and hopes that her father will see it as an individual decision and not a reflection of their generation. Yuriko appears in Gakurouta's mother's Kimono which briefly stuns Gakurouta, not because he is attracted to her but more of a shock at seeing it worn in the flesh (I am assuming that Gakurouta's mother died when he was young). Now in the safe confines of their car, the 2 lament the difficulty in dissociating with family and both confess being more at ease in each other's company than that of their family.

On the way home, Gakurouta and Yuriko stop at a nearby shrine to pray for the upcoming year. They aren't the only ones doing this, as while queuing for access to the shrine altar, Yuriko is spotted by Cindy - the girl who got lost in Kochi. Cindy is chased down by her father, but not the one we saw back in Kochi and to further hint at her parent's relationship, she calls this one "Papa" (Cindy's parents are gay if you haven't worked it out). Cindy's Papa apologises for his daughter's behaviour and thanks her for what she did back in Kochi, before heading back to his husband with Cindy. She tells Gakurouta about this encounter as well as how happy her parents looked together, which makes her think about what exactly is a marriage, as there are couples that could get married, but can't because they are in a same-sex relationship and right now (even at time of writing) same-sex marriage is illegal in Japan. For example, Shou is permanently moving to England because there he can marry Gilbert (same-sex marriage has been legal in England, Scotland, and Wales since 2014 and since 2020 for Northern Ireland) and raise a family, which he wants and what is the point in a system that prevents people from getting married because of the sex of their partner. Gakurouta agrees with her frustrations as if same-sex marriage was legal and acceptable in Japanese society, he could have confessed his feelings to Sousuke, get rejected, cry for a bit, move on and fall in love with someone else but instead his true feelings must stayed bottled up out of fear of being not only rejected by who he loves but by society as a whole.
Gakurouta begins to cry and they move to bench where Gakurouta recovers and explains his stunned reaction to Yuriko wearing his mother's Kimono. He has always felt in order to be happy, he needs to be like his parents in a 'normal' marriage with a 'normal' family, but obviously he can't have a 'normal' marriage with a 'normal' family. Gakurouta sees marriage as a system that ties two people together for better, for worse, for richer, for poorer, in sickness and in health, to love and to cherish, till death them does part and for most, loving the other person romantically is a great motivator, but romantic love is not the only motivator as one can get married to not be alone, to shelter each other from the world, for work or for friendship, or to eat a nice meal with someone.
This marriage philosophy conversation is interrupted by Sousuke calling Gakurouta, who has found their cover story papers after he went into their bedroom on the request of Take, so wants to know the the truth about their relationship. Gakurouta explains that they are legally married and neither loves the other romantically or sexually, but they have promised to be together for better, for worse, for richer, for poorer, in sickness and in health, till death them does part. The concept of marrying someone you don't love is alien to Sousuke, but before he can explain himself further and convince his friend to stop this 'madness', he gets stabbed in the hand by a box cutter that is wielded by his ever-increasingly mad girlfriend.

The chapter starts with Sousuke imagining Gakurouta and Yuriko walking in a different direction from a crowd of people lke they are a penguin in a Werner Herzog documentary. We then return to the present, just after he has been stabbed by Miho, his probably soon-to-be ex-girlfriend, now lamenting at another failed relationship. It then flashes back to few hours earlier as Take cashes in the ignorance she had feigned after Sousuke and Gakurouta had accidentally broken or damage things inside the house (like vases and walls) when they were playing and gets Sousuke to place an amulet that is imbued with the power to increase the desire to have children in their bedroom and there he finds the couple's cover story documents. We then return to a slightly closer-to-the-present-time Sousuke, who is reminiscing about school reunions and how for every one of them he was part of a endangered species with dwindling numbers - a bachelor. Also, he saw all of his classmates and friends look incredibly happy as they gushed about their partners and children and hated how he could never achieve the same feelings. His friends and classmates aren't too bothered by his inability to stay tied down - after all he doesn't know what a 'normal' marriage and a 'normal' family are. We now are definitely back to the present (I swear this series jumps forwards and backwards in time more often than Doctor Who) as Sousuke identifies internally where the relationship with Miho died and it was when her smile that he loved to see, seemed to demand 'something' from him and he was not going to be able to provide it. Sousuke is resigned to his death, as he believes that the happiness he wants is unachievable for him and he stands there as Miho lunges at him, box cutter first.
Immediately concerned for their friend, Gakurouta and Yuriko head home, only to head to the general hospital instead after Gakurouta ends a call (Yuriko is driving) with Take's caregiver, Sugimoto, as Sousuke only has injuries to his palm and left arm as Miho didn't actually stab him, but instead stopped at the last second and has been unresponsive since (police have been called). They arrive at the hospital and Gakurouta heads inside to Sousuke and while Yuriko goes off to find a parking spot as well as find a moment to breathe, the boys talk about Gakurouta's marriage and right now Sousuke is more hurt that Gakurouta didn't immediately tell him the truth than from his physical injuries and still doesn't understand how you could marry someone you don't love. He has never head about political and arranged marriages, has he? There is virtually no love in any of those relationships (certainly in fiction) and those are the heterosexual examples. Gakurouta confesses to Sousuke that he is in love with someone for pretty much his whole life, but he cannot be with that person nor can he get rid of these feelings and because of this, he was going to be unhappy for the rest of time. However, he met Yuriko, who was easy to talk to, listen carefully to what he said and most importantly, treated his unrequited love with care and dignity. This revelation made him realise all the pain associated with the love is born from society and its norm, not the love itself and being at the side of his love was all he needed to be happy. He believes that both of them grew up expecting to be like everyone else to achieve happiness (get married, have kids, etc), but instead what works for thee, does not have to work for me and we define what happiness is to us. Sousuke friends and sister come rushing in to check on him and are relieved that he is ok. Gakurouta sees this as the opportunity to leave but as he does, Sousuke asks if he can visit Gakurouta sometime, with intention being to him of which he can (also it is implied that Sousuke put 2 and 2 together and worked out who Gakurouta's mystery crush is).
Gakurouta meets up with his wife (who has changed out of her Kimono) and both their stomachs growl, so they decide to get lunch and eat it at home, with suggestion being sushi, although one of them doesn't like sushi as they aren't fond of sushi rice (sashimi is ok though).
There are 2 bonus chapters with the first detailing Shou and Gilbert meeting up in an airport in England (doesn't specify which, but most likely Heathrow or Gatwick) where they kiss and discuss their living arrangements for the immediate future (Gilbert's room-mate has temporarily moved out and his now with his girlfriend) as well as what to do next.
The second bonus chapter takes place a few years later and Take has finally got her wish and died, while Gakurouta and Yuriko are moving out of the family home and are going to be running it as a share house, with a section for remote work. This is all being explained to Shou by Yuriko via video call and Gakurouta had some trouble with the process (from I assume a then still living Take, as there is literally no other blood relative alive) and was also concerned he might lose his connection with Sousuke and giving the home that has been in his family's hands for generations, but obviously has warmed up to the idea. Yuriko ends the call as she has a flower viewing party with her husband, Sousuke and his friends and Shou has to got to bed as his son came to his room to say goodnight. This either must be some early morning flower viewing party, as England e is about 8/9 hours behind Japan as Daylight Savings Time, or British Summer Time, for the UK begins on the last Sunday in March and while it is not explicit where exactly in Japan the series takes place (we know it's not in Kochi) but a good assumption would be Tokyo and the cherry blossom in Tokyo starts to appear around 3rd week of March. The alternative Shou and Gilbert are irresponsible parents by allowing their child to be up so late that is technically the next day, TLDR; the author probably forgot how/didn't know far behind the UK is compared Japan with regards to time zones.

Theme-wise to me, this feels like 2 different series in 1, as the first 2 volumes are a slice-of-life romcom without the 'rom' and the final volume is more about the expectations that society (specifically Japanese society) has about marriage and married couples. This disconnect feels like the author suddenly remembered for the chapters in volume 3 that the main characters are LGBT+ and are married, which is something that same-sex couples can't do in Japan and thus must complain that society denies them their happiness. Another example of this disconnect is the dropping of Gakurouta's 'perfect husband' attempts and while volume 3 takes place at the end of December, he was still referring to his "how to be a good husband" book around September/October of that same year. Another problem, that specifically relates to volumes 1 and 2, is Gakurouta's and Yuriko's inability to communicate the basic things such as likes and dislikes (they literally discuss how to answer the 'who does the cooking' questions but not the IRL application of it) and while both have reasons for not being forthcoming on private details (people don't understand Yuriko's inability to not fall in love and Gakurouta has spent half his life in love with a man and cannot tell anyone about it for fear of society rejecting him), only one makes an effort to get to know the other, Gakurouta, while the other tries their hardest to not let the other get involved. Another issue I have with the series is its age rating from Yen Press, the English language publishers of the series, who give it an older teen rating, making it suitable for those 16+, but beyond references to a genre known for its sexually explicit scenes, it certainly suitable for those 13+ (there's more physical violence with actual injury in Nisekoi than ths series).
Overall, I think the series is probably a 6/10 as I enjoyed the theme of volumes 1 and 2 as well as the plot, despite my issues with Yuriko, but the complete shift in theme for volume 3 is off-putting for me. While I have no issue with volume 3 nor its contents, I prefer the first 2 volumes and I assume it's not best practice literature-wise to change theme two thirds through your story.