Wow... there's a lot written about the ending. I actually read the manga twice over once I got to the ending, primarily because I'm an emotional nerd.
Be that as it may, I will now prepare to offer my defence of the reasons why the current ending is, in fact, the best ending. First, a look into some character profiles:
Manaka: Many people have commented on Manaka; his weakness, indicisiveness, his underserved popularity. Could it be possible for three amazingly desirable girls women to fall in love with this "loser?" Possible, but in the real world, not likely. However, that's why this is fiction. Having said that, Manaka's character and actions in response to this unrealistic situation is not, in itself, unrealistic. First of all, Manaka is extremely insecure of himself, particularly in regards to girls. (Being a grad student, I can offer references to volume and chapter, if anyone so desires, but on this point, I don't think anyone would disagree). Second, Manaka is, perhaps overly, concerned about other people. This is not a good combination for confessions. These types of people are not only concerned with their own emotions, but also think about the impact their confession would have on the other party, such as, "would my confession become burdensome to her?" However, when a quick decision is required, Manaka acts. This is one of the points of attraction for the girls, that he is reliable in dire situations. It is when he is given a chance to think too much. Fourthly, he is cerebral. Finally, he is honest, or at least tries to be.
Now how do these character traits explain his actions? Simple. First, in terms of his indisiciveness in picking one girl. Exhibit A. He doesn't really understand, and most of us would agree, why any of the girls would actually be attracted to him, so has trouble believing that is the case. This is what limits his relationship with Toujo, and why Nishino and Satsuki needed to confess to him first. (The reason why he confessed to Nishino is that he never believed she would agree in the first place. Afterall, it was only because of his friend's prompting that he experience the same rejection from Nishino.) Exhibit B. He is afraid of hurting the feelings of the girls he doesn't choose (thereby tacitly rejecting), not understanding that not choosing at all hurts them even more in the long run. I think eventually, he understood this concept. As stated before, in fiction, unrealistic situations occur to realistic people. Case in point, BAD TIMING. When Manaka tries to clearly reject Satsuki by not accepting her present, she ends up being even more hurt. It was bad timing on his part. Rejecting a carefully thought-out (at least, Satsuki thought so... I'd never wear those boxers) present is not the right time. However, this would reinforce his idea that rejection would just end up hurting them even more. Exhibit C. In terms of his own heart and feelings, Manaka likes all three, not equally, but in varying degrees which are proportional to his confidence of them liking him. Satsuki, he likes the least, and not so much romantically. However, she is the most clear about her intentions. This is your small gain/low risk scenerio. Toujo he likes the most, but is the most unsure of. And because Manaka is an honest person, he feels it would be wrong for him to be in a relationship with someone without clearly understanding his own feelings. Others (most people, I would think) would approach a relationship as a way to find out how deeply their affections may run. I agree that if Toujo had just made her heart clear, then Manaka's decision would have been easy. But that goes against her character (which I will evaluate later).
As for why the girls would be attracted to him, I still ponder, but here are some reasons why. 1) Because one girl likes him, he instantly becomes more attractive to other girls. Girls may argue with me about his point, but I think real-world experience would support this theory. 2) Considering his personality, he will more likely be courageous in regards to others' benefit than his own. He would not stand up, I think, to defend his own use of booksmarks with half-naked idols, but when his friend is being attacked, he would stand up for him. To certain small percentage of the female population, this is a desirable attribute. 3) His passion towards his dream. When he talks about film-making, he losing much of his awkwardness and insecurity. I think this is what initially attracted Satsuki and Toujo, and what deply affected Nishino later on. This is attractive to women, a man with a clear goal. 4) The paradox of women and echiness. I think his resolve in not taking advantage of the girls in ecchi situations is a point of attraction to the girls. This is a paradox, however, because at the same time, the girls want him to be ecchi with just them. It is similar to how a man might view a girl who is "pure" and be attracted to her, while desiring to be the one to make her "unpure." 5) As meantioned before, Manaka also has impactful interactions with all the characters within the manga. He is the catalyst for the character development of all the major characters. Although he himself remains static until near the end, he changes every other character, both major and minor, both directly and indirectly. Even his soccor friend, Ookusa, is affected. His attraction towards Nishino and his inability to understand why she isn't attracted to him. 6) A final point of attraction, most assuredly for Toujo and Nishino, but maybe for Satsuki as well, is Manaka's concern with the "inside" of a person, and not the "outside." This is why Toujo loved him, because he was the only one who was considerate of her before her awakening as a swan. This was also a reason why Nishino loved him, because he could see beyond her looks. This is also one of the areas of major insecurity for Satsuki, because she felt she couldn't compete with Toujo or Nishino on the "inside."
In conclusion, I don't think it's too unbelievable that any one of these girls would feel attracted to him.
Toujo: This girl is tragically interverted. That is the most major aspect of her personality. Next would be her own insecurities. Having grown up all the way through middle school as the "ugly girl," she can't help but think that she still is that way. She is also, obviously, very intelligent. However, she also lacks perception and insight into other people. Like Manaka, she is considerate of other people, often times at the sake of her own benefit. Her character changes first as a result of her encounter with Manaka, but otherwise, remains static until the end. As many mentioned, she is the most like Manaka himself in many respects.
Now as to some of the motivations for her actions. First, her love for Manaka. I think that her love for Manaka is actually, at least in part, a form of hero worship. She sees Manaka as the one who brought her into a new world where people appreciate her. He is her confidence, the actualizer of her dreams. Contrary to what some others have written, I believe that she would not have pursued a writing career if not for Manaka's suggestion. She never showed her writing to anyone else, until Manaka read her novel. At Oumi, I believe she would have pursued an academic career, not in liturature. Perhaps, later in life, or as a result of her brother's constant pestering, she would have submitted a piece of her writing and her talent would have been discovered, but this is doubtful, since she was not affected by his support prior to meeting Manaka.
Her lack of self-confidence also shows in her decision to follow Manaka to high school. It is his passion to make movies with her scripts which gives her confidence to write more. She would need this confidence in order to move further in her pursuit of writing.
As for why she never confessed to Manaka, first of all, she thought that Manaka and Nishino were continuing to date well into high school. As such, she tried to openly deny any attraction to Manaka beyond working together, while continuing to harbor love for him. In her mind, she would support Manaka and make him happy. This, of course, would lead to much confusion on Manaka's part, as his appreciation for Toujo's talents deepens into love. Later on, she would be envious of Satsuki's overt sensuality and Nishino's history with Manaka. Such insecurities would cause her to confuse Manaka constantly, as one moment, she seems to have a deep passion for him, while the next, turning a cold shoulder. Perhaps, in a way, it would ruin her ability to write if her muse became human.
Because I feel that Nishino's character was best developed, I will proceed to examine Satsuki. She is, without a doubt (well, maybe barring Kurogawa sensei), the sexiest of the girls. She has much confidence in that, and perhaps had some experience with other guys. However, she lacks confidence in other areas, primarily, in any area that doesn't involve her body. Granted, she and Manaka speak the most naturally with each other. However, even she understand that is not the basis for a romantic relationship.
As for her reason for liking Manaka, this one I understand the least. Perhaps, and I conjecture here, it is because no other guy made her feel normal. She admittedly has the most fun with Manaka. Perhaps other guys were so intimidated by her looks that she never felt quite human with them. Also, as I meantioned earlier, it may be the very reason that he seems unattainable the he becomes attrative to her. Any other guy would fall drooling at her feet, so why doesn't he?
As for why she was doomed to fail, it was because she believed she would fail from the start. She was the last of the major three girls (I don't include Yui because there NEVER was a development of romantic feelings between the two) to meet Manaka, and she knew it. She also knew she had the least in common. So her greatest insecurity was her place in Manaka's heart. This caused her to react defensively, overly aggressive. It would have been to her benefit is her strategy had been more subtle. Case in point, in volume 9, when she said, "If I ever felt like it, I could easily attack you," she had great impact on Manaka (who wouldn't be, in that situation?!?!), causing him to desire her, and not the other way around. However, playing from behind caused her to make mistakes which would inevitably play her downfall. If, instead of forcing kisses from Manaka, she would, for example, look at him trapped under her, almost brush his lips, but instead, smile and run away, I think Manaka would have been more likely to start desiring her. Alas, men's heart are wired in such a way that we desire most the things which we seem the least likely to get.
Finally, we come to Nishino. She has the most development throughout the manga, and is realitvely consistent with it. Since her character changes the most, I will examine her character as it changes. We know from volume 1 that she was not like other girls. Her tastes in guys were very particular, even though she was wildly popular. In fact, it is alluded to that she hadn't had a boyfriend prior to Manaka for some time (we know, at least, that she never confessed to anyone other than Manaka). We also know that, while the things which attracted her to Manaka reveal much about her character, in many ways, she had no ambitions. She wanted to go to a particular school because it was closest. Think also her eagerness to go home to eat her mother's pie. We also know that she was willing to become physically intimate with Manaka relatively early.
As for her reasons for liking Manaka, I think the Mangaka made that clear on three occasions (at least to start with). First, though not coming until much later in volume 9, was how he stood up for his friend. Even then, he impacted people around him, as he ran 50 laps and people were cheering for him. This aspect of Manaka was attractive to Nishino. Second, in volume 1, was Manaka's attraction towards the inner characters of a girl. Third, was his very creative (well, Toujo's creative) way of confessing.
Her attraction for Manaka was somehow strong enough, or deepened enough, that, even though she noticed the budding mutual attraction between Manaka and Toujo, she desired to continue pursuing him.
As for her reasons for choosing to go to Oumi, I agree that it was not soley based on letting Manaka go to Izumizaka. I actually think she saw how Manaka and Toujo interacted, and realized that she herself didn't have a dream. This made her want to have a dream of her own. She understood that, in terms of trying to follow Manaka in his dream, she would never be able to compete with Toujo. This is a major character development from who she started off as. Their Middle School relationship also showed that she was willing and able to get Manaka to move forward when he was stalled in his insecurities.
Having now gone to seperate High Schools, Nishino decides to dump Manaka. However, his willingness to come to her defense makes her more attracted to her. However, as she continues to see him interact with Toujo and Satsuki, she makes another decision which shows her character development. She dumps Manaka. Not because she stopped liking him, but because she understood that she was not the one that Manaka liked the most. Had Satsuki been in that situation, she would never have dumped him, using her relationship with Manaka to improve her chances. Nishino, likewise, should have known that dumping him would be a huge disadvantage for her, and yet she does. Why? One possible reason is self respect. She didn't want to further carry on a relationship with a guy who loved another girl. Another might have been for Manaka's sake. She understood that Manaka felt guilty liking Toujo while dating Nishino. Manaka also would not have dumped Nishino because of his character. Therefore, Nishino freed Manaka from that burden.
The next character development occurred on valentines, when Nishino, after finding a dream to pursue, makes chocolates and leaves them at Manaka's door without a card. She never expected Manaka to know that it was from her. This shows that, while she still loved Manaka, she didn't want her love to, once again, be a burden on him. However, because of the misunderstanding with Yui, she comes to think that Manaka still cares for her.
However, it seems that she was willing to let it be as a one-sided love. Even when, by chance, she meets Manaka at night, she give him advice towards his future girlfriend and ends to encounter quickly.
Their next encounter deepens Nishino's love for Manaka, as he defends her in front of her fanboys. And later, because of another chance encounter, they start seeing each other regularly after work. Nishino realizes at this point, that, in terms of competing for Manaka's heart, she should have gone to the same high school. But she also shows the depth of her interest in Manaka, because she started watching many movies in order to better understand him.
Her desire to participate in Manaka's dream is fulfilled when they cast her as the heroine of the next movie. You get the sense during these times that Nishino is struggling with her attraction for Manaka. She thinks that she doesn't have a chance, so has decided to let Manaka go. However, circumstances keep thrusting them back together. It was during these times, I think, that Manaka's love for Nishino also deepened. I think NOT dating Nishino endeared her to him more than when she was dating him.
The next encounter that showed Nishino character (whether it was there from the beginning of developed later, I can't say) was when Nishino invited Manaka over to taste her cake. Here, Manaka spies Nishino in the arms of Higure, and misunderstanding it, runs out. This is a critically element of Nishino's character which made her the right choice for Manaka at the end. Instead of avoiding the awkwardness of the misunderstanding, she confronts it directly. Even after she tried to probe Manaka about it, he, coming to his own conclusions, and as a result of those conclusions, seeing it more proper to let Nishino go, avoids the situation. So does she let it stand? No, she goes to his house and confronts him directly. Had that been Toujo (think of the misunderstanding with her brother), the relationshp would have been over right there. Instead, she takes it as an opportunity to, once again, affirm her love for Manaka.
By this time, I think Nishino had set within her heart to love Manaka again and get back into the competition. On the next encounter, she should her concern for Manaka's happiness again, when she returns to the building in order to retrieve his prized possession, his camera. Then she waits for Manaka, to fulfill his promise to take her out after the party. Here, she makes clear her feelings for Manaka again, and her willingness to carry that out intimately. Unlike Satsuki, Nishino lets Manaka be the aggressor, while making plain that she desires it.
Here, I think the Mangaka gives us the biggest clue of all who Manaka will end up with. When she tells him of the first time she saw Manaka, Manaka realizes that, contrary to his understanding, his relationship began with Nishino first, because Nishino was the first to see the attractiveness in him (although she forgot about it promptly
Later, when Chinami comes on the scene, once again, Nishino doesn't allow misunderstanding to creep in. This time, however, it is Manaka that comes to Nishino, perhaps because he knows that she would be concerned about it. Once again, had that been Toujo, she would have assumed that what she saw was correct and never broached the subject.
She shows the next development when she shows that she is taking pastry making seriously. Instead of waiting till later, she talks to Manaka about her desire to go to France. Henceforth, she is constantly reaffirming her love for Manaka while giving opportunities to ask her to stay.
Next, when Higure is setup as Nishino's fiancee, she clearly states her intent to Manaka. Here, I feel Nishino would have gladly done the third movie, if only Manaka had asked. However, since he didn't, instead of moping about it, she asks him to go on a trip with her. She is bold in asking Manaka to do something that is clearly selfish, yet also opens up her heart to him during the trip, confiding her difficulties with pastry making. None of the other girls had done either asking or telling.
She continues to be very clear with her feelings towards him, culminating in her confession on the pullup bars. If nothing else sealed the Mangaka's decision on who would be Manaka's girl, then this use of paralellism should.
When Manaka was feeling down, while talking with Nishino, she queried him about it. And then she told him to depend on her, as she depended on him. This is what is involved in a recipricated relationship, and I think this is the final element which tipped Manaka's heart towards Nishino. Interdependancy.
Here, we get a peak at Nishino's insecurities. She still feels that Toujo is highest in Manaka's heart. When she sees Toujo's confession in the film, she rightly interprets that as an honest confession. We see a little bit of her wickedness, when she meets Toujo and her brother at the fair, when she asks if he was her boyfriend. When she reads Manaka's reactions to Toujo, she confronts it again, instead of avoiding it. This forced Manaka to really examine himself, and forced him to "man-up" to his decision, until finally, he comes to Nishino, and confesses again and tells her he told Toujo ab out their relationship. I think it is at this point, that basically, the question of who is over. From this point on, it's Nishino, and no one else. The rest of the story is tying up the loose ends.
Now, after all this, (wow, what a grad student nerd I am) Why did Manaka break up with Nishino again at the end, and why did Nishino go to France after all. Here it is. Maturity. Love is not one life following after another. Love is the pain and difficulty of two lives joining together. Nishino needed to establish her own identity, apart from Manaka's girlfriend. This is the same for Satsuki and Toujo. Therefore, in order to pursue her dreams, she went to France. Had Manaka asked her to stay, she could have continued in the pastry world there, it is true. I think, ultimately, if Manaka had asked her to stay, she would have, although not without trepidation. It was a decision that had no easy way out. Go to France, give up Manaka. Stay in Japan, give up a great opportunity.
Now as to Manaka's decision, it is because he finally matured as well. He understood that he was as yet not mature enough to make the right films. I think he also wanted a chance to change and become a man worthy of Nichino's love. Also, he wanted a chance to seperate from the confusion of being around Toujo and Satsuki. Would I have made that decision? No. I would be worried that Nishino would realize what a loser I was and find some hunky guy in France. I would have asked her to stay, continued our relationship, and probably not have been invited to work at that film company. But since it's fiction, then their love was strong enough to carry them through their time of seperation.
Finally, the allusion Manaka makes about Toujo's novel at the end. This doesn't mean that Manaka still has feelings for Toujo. It means, as he stated when he told Nishino he wanted to start over again, that he was in love with her novel. He thought in order to honor all their time together, he needed to bring her novel to film in a proper way.
Anyway, enough with my rant. As you can tell, I really like Nishino. In fact, I can say that she is my favorite Manga/Anime girl ever. Yet, I have never met anyone like her, and don't expect to. But it was a fun ride.