You haven't proven anything. Your only argument here is that there will be more games after KH3, therefore KH3 can't be seen as the "conclusion" of anything--when in fact it is undeniably intended as the conclusion of the Xehanort saga and everything that happened within that saga. What comes next are new plotlines.
Where did I say it can't be seen as the conclusion of
anything?
Don't twist my words man.
KH3 is the conclusion of the Xehanort plot line specifically, this does not mean that it is the conclusion of the bonds between the characters—this being significant of the characters having more story to be told past this arc's ending. If KH3 was intended to be the last game featuring these characters, I would agree that this game's necessity of tying up loose ends would be warranted. But, as the characters are carrying over into the next plot line, so is their characterization and character relations, which are still susceptible to growth and change. If you want to believe that it won't be hit on, that's fine, but this holds no bearing on it still being a relevant factor there to be dealt with still.
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(TLDR: Sora/Kairi's potential romantic development is fine in my eyes, Nomura's writing is strange at times, and I'm out of this, but this was good chats)
Anyway, to add as a final note for myself in this thread, I just don't see why ultimately, it is such a huge issue here in this gauge of the aspect of what we're considering canon in appliance of the word. The usage of "canon" and "confirmation" for Sora and Kairi being by the action of dating or the actions/dialogue that clearly state a conscious acknowledgement between both parties of romantic feelings for each other—this is honestly reasonable, actually. Especially if the expectation is that of traditional romantic stories that usually results in these type of climactic, concrete expressions. But, the usage of "canon" also applies to how Sora and Kairi's distinguishing friendship has shown moments/signs of specific romantic implication about them in the series multiple times, including even just a simple paralleled credit scene in 2.8. Romantic subtext being used to represent their relationship deems this statement true, whether one personally finds those moments to be a big deal or not. It is also true, that KH3 didn't emphasize explicit romantic actions between them. Can't deny that either technically, especially if abiding by the expectations above. Yet, another truth, is that KH3 didn't emphasize explicit platonic actions or fully negate the existing romantic undertones that have been associated with their relationship up to this point. We're still stuck in the same state their relationship has been in, and from my perspective, KH3 did a good job in representing this current bond regardless of whether one wants to see their interactions as an emphasis of friendship or romantic nature.
I for one believe its great that the moments between Sora and Kairi are actions/dialogue that fit along the spectrum of both romantic and platonic meaning, as this fits the current expression of their relationship of friendship+romantic undertone meaning. One could spend hours and days here arguing and analyzing all the contextual/subtextual moments between them in KH3—whether some moments reflect common romantic tones used in storytelling for how the scenes played out, or, if their moments were all, without a shadow of a doubt, strictly platonic actions. I have no interest in doing this back and forth anymore, but I will stand my ground, strictly speaking to the moments expressed between them, that these two characters represented their current bond quite well from the interactions or dialogue they do have about each other (aka, including where each other isn't present). All their moments, all the way up to their final scene together and how it was structured doesn't negate the openness of romantic possibility that has already been set to them by the context—the context of their specific relationship giving us the understanding that these actions between them are open to romantic influence. I know very well that some people would argue that the tone/atmosphere in their final scene was conducive of common romantic motifs as they watched it unfold—both basked against the sun as they sat on the tree where they shared a moment that signified that their hearts are "intertwined" (which, the actual scene supports this meaning in both japanese and english text, still, the Paopu Fruit isn't strictly romantic or platonic), their hands in contact with each other as they sit there, a close up of Sora adjusting and securing his hold onto her hand as they retain eye contact until he disappears, Kairi left showing tears and dejection from this. A lot of people would have no problem recognizing this scene as being influenced by romanticism, being convinced that this, at the very least, has every right to be open to romantic interpretation if the context deemed it to be fitting. Then, some are convinced everything about this scene is purely, without a doubt, platonic in nature since the actions themselves aren't strictly platonic or romantic, and Sora has held other people's hands in different contextual situations all together. Then of course, some don't give a shit at all about any of this because everytime they see Kairi now their eyes turn bloody red with rage at her overall usage in the story—romance or platonic means nothing if this is what her character amounts to in the story. It's all over the place with the KH online community, expectantly so, and there are certain amounts of merit to all cases.
With Kairi and Sora's relationship still being static with friendship+undertones of romance status, personally, I find this scene to be an acceptable way of emphasizing the closeness the two characters share—this being the very least of what I could say about it along with the other scenes between them. I will stand that in my personal perspective, it just doesn't make any coherent sense that if Nomura's goal was to make Sora and Kairi's relationship in this game strictly platonic, with no doubt of romance not existing between them, that all of their scenes together in this game would've played out the way that they did—with actions that aren't strictly platonic in nature, and without addressing the change and negation of any romantic feelings anymore between them in the context of the game. I can't fathom that line of thought or writing "consistency". It makes no sense to me. The only way that I can understand this with the information that we have in certain truths of the context is that it possibly was the act of sharing a Paopu Fruit itself—and in extension, the overall Paopu Fruit representation that other characters now share since KH1 (BBS trio, Sora and Riku—both under platonic nature by the context)—that Nomura was particularly worried about receiving a strictly romantic tone in an absolute sense. That, rather than completely setting their specific relationship to not having any romantic undertones at all anymore. If that was the case, it'd make more sense considering that, unlike all the other actions displayed between Sora and Kairi, sharing a Paopu Fruit has been commonly deemed as a strictly romantic action by a good chunk of the fanbase since this action alone is represented by Sora and Kairi primarily. With how much has changed since KH1, being attentive to the Paopu Fruits overall meaning and presentation seems warranted at this point.
(Also, quick note about the Paopu Fruit representation of Sora and Riku, because I didn't respond to it earlier: Their connection with the Paopu Fruit and Dearly Beloved is still explained by the best friend nature of their relationship—none of these two things represent a strictly romantic value or deviation from platonic meaning. Dearly Beloved, which title-wise represents love in general, being used to represent their hearts being in tune with one another doesn’t imply a change from them being best friends (Mickey even implies this is due to their friendship anyway), this being the same way that eating a Paopu Fruit, which signifies their hearts being intertwined, wouldn’t change a friendship either since it isn't strictly romantic. For Sora and Riku, these two ideas seem to purposely correlate with each other by showing that their combined (intertwined) Keyblades have the Paopu Fruit keychain—showing how their hearts are indeed connected just as the legend says, and just as Mickey pointed out with the usage of Dearly Beloved. However, when it comes to the act of sharing a Paopu Fruit, this is still something that is mainly represented by Sora and Kairi.)
Overall, about all that and his writing: I don't know. And, Nomura needs to be better at writing. Maybe these are truths too. Ugh. Anyway, the overall meaning of their relationship entering KH3 remains the same going out of KH3. It didn't shift, all we got was more showings and interactions of their close bond—which this isn't bad, but it isn't necessarily advancing them past the current status either. Rationalizing that they have shifted from their established relationship just because Sora didn't do the exact same damn things he did in previous games, like think about her on the journey, has no bearing on what HAS been done between the two of them in the game. It's like confirmation bias is guiding that sense of judgement in Sora and Kairi's disposition. No. If their relationship is represented in a way in a story narrative, this doesn't change unless the change itself is signified—this is literally applicable to any and all unique relationships. With all the interactions that Sora/Kairi do have in the game, there's no rational reason to believe the change of complete omit of romantic feelings in their relationship has already occurred. Whatever change is (or won't) happen to their current relationship, hasn't happened yet, which isn't implying that it won't at all. Simply stating that a character CAN change does not mean it has happened yet, or even, that change is even expected by the context. It's simply going to be a series of speculation until the story shows us more.
There are multiple perspectives, multiple angles of rationalization that all fans will have to personally understand, describe, and feel about these scenes between them. And, that is fine, and completely necessary for the expression of self thought. I'm cool with it. But, no matter what I think, no matter what you think, no matter what Jim down the street thinks—there are still certain truths that the context retains besides our own thoughts, and right now, it's that the friendship and romantic aspects of their relationship is still open to be dealt with by Nomura as the story and characters carry on into the next saga. Free to be expressed, free to be completely negated out of existence of possibility per the context. Or, free to be ignored with no change whatsoever, which sounds very much so like him. Even then, this would still only mean that their relationship has continued to only reach a limit to being represented by a strong, tethering bond of friendship and subtle romantic portrayal. Ultimately, especially with Nomura's writing style and ability, we'll see how everything plays out at a later time. I've enjoyed this conversation, but I just can't add any more with this just being the extension of my side on all this.
This was good though, at least to me anyway.