As HeartSeams so kindly requested I shared my insights on the matter and I'm in the mood for a good rant...
Yes. Most definitely. If not gay, then they're at least Bi-sexual.
I'm talking - Sora and Riku. Lots of Kairi references as it helps prove the point.
I mean, look at KH1. For better or worse, Kairi doesn't really play a role. I mean it. None; zilch. It's all Riku and Sora and their issues.
Now, Sora's an affectionate guy. He befriended Donald and Goofy well enough, opened up to basically everyone he met, even tried reaching out to Xemnas. So of course he'll be worried about Kairi, a girl he's known since childhood.
Let us review Riku's reactions in both times Sora asked about Kairi:
1) "Kairi's coming with us!" While reaching his hand to Sora, with Kairi nowhere in sight, a storm raging, the island's being torn apart, and Darkness is covering the both of them.
I don't think Kairi's coming.
2) "She might be looking for us now!" Either he was really trying to get Sora to not worry about Kairi - which either in the positive or negative aspects of this, is a lot more Riku-Sora than Kairi oriented, or he was really good at acting stupid, seeing how Kairi has zero fighting abilities we know of save beating up Shadow Heartless with a Keyblade Riku gave her, in a universe currently crawling with Heartless, and most likely no transportation abilities.
This is followed by "just leave everything to me". I can't imagine he wants Sora to worry too much in the sense of bother.
And of course, the crown jewel - Maleficent making it quite clear in 30 seconds or less Riku has one insane jealousy issue when Sora's involved. Screw Kairi - Maleficent was telling Riku Sora didn't care about HIM anymore. That he replaced HIM. That Sora's new friends were better than RIKU.
It seems that as far as Riku's concerned, Kairi doesn't play a part. Don't believe me? Fast forward to Monstro and Sora's refusal to kidnap Pinnochio even if it means they might save Kairi.
"You’d rather fight me? Over a puppet that has no heart?"
One might think that at this point Riku should be furious Sora'd abandon Kairi, but that doesn't seem to be the case. The issue of their argument is that basically, Sora chose someone else over Riku again. And if we REALLY want to go the distance, you can argue the puppet that has no Heart is actually Kairi at this point. But even without it, Riku's once again basically saying "you prefer someone else over me".
That makes it quite logical that by the time we got to Neverland, he was basically rubbing it in Sora's face, how Sora's a horrible friend.
"Are they that important to you? More important than old friends?"
At this point you can think he's talking about Kairi, but as I'm hardly the person to take scenes at stand-alone, face value, I remember everything I ranted to you up to now.
'Old friends' would also include - Riku himself, as he's an even older friend than Sora. Kairi, after all, came to the islands a year after BBS, and we all saw what happened in BBS with SoRi. So Riku falls under 'old friends'.
So why bother, you say? Why should Riku carry Kairi around, seemingly cause Sora to feel concern about her, make him worry?
Well, we already saw that Riku was, most likely, jealous of Kairi when it came to Sora since Sora kept asking about her.
So if 'old friends' like Riku aren't important to Sora, he'll hurt him where it hurts most - with another 'old friend', one that Sora asked about.
The thing is it's not even so much saving Kairi at this point as much as it is humiliating Sora, taking Donald and Goofy from him, and the Keyblade as well. Leave him with nothing at all, and Riku as the ultimate winner.
Ties in well enough with his will to be free, I think. Even if it's to be free from Sora. And what better more is that Riku would dump him before Sora'd get to hurt him more. Splendid.
And I do hope I don't need to explain in future installments why Riku's basically gay for Sora to the point of obsession. He's the one Zexion bothered appearing to Riku as to hurt him where it hurts most; Sora's the one who Riku agreed to eventually dirty his hands for and even succumb to the same Darkness he hated so much, if it meant waking him up. And Sora was the one who, despite it all, kept running into Riku because Riku couldn't really stay away.
Let's face it. The games showed me basically no reason why Riku should've stayed behind in KH2 when Kairi asked him to (as he testified in one of the speech-bubbles). Only one - Sora. And it was wanting to be reunited with Sora that won over Riku's will to not be found, making him stay around for longer each time.
Oh and almost getting killed saving Sora from Xemnas. Another beautiful moment. Mmhm.
Well now; that was Riku.
What about Sora?
As I stated before, Sora's an affectionate guy. He befriends flea-ridden lionesses and blonde girls about to be beheaded he just met and saved. So what makes Sora's treatment of Riku, special?
Well he did declare him his best friend and stated that he liked him, even as an adorable innocent four year old.
Also, in some of the aforementioned quotes, Sora's responses also disregard Kairi. Pinnochio is a clear case. Not quite saying Sora doesn't want to save Kairi, but the focus of that scene remains, now and forever, Sora and Riku's own conflict. Riku's the one in the wrong, and even if it means hindering saving Kairi, Sora wants to set Riku straight first.
To top it all, Sora's concern towards Riku is a constant motif throughout the game as opposed to his mentionings of Kairi who split into 1) bursts of nostalgia caused by the fact her Heart's in his Body, and 2) times where he might as well have been thinking about Alice for all the proper establishment presented. As we said - affectionate guy.
And of course, the #1 reason why I can "forgive" Sora's mistreatment of Riku in KH1 - he had Kairi's Heart in his Vessel. Those of us who finished Ven's scenario in BBS know well enough that Ven's Heart being in Sora is a great cause to why Sora is as we know him. Granted, the bond between the boys' Hearts seems to be deeper than between Sora and Kairi's, but it's a bond deep enough to spawn Namine.
Excuse me if I can't REALLY believe Sora was acting fully on his own behalf during KH1 when Kairi was concerned. Hell, this might also in fact explain some of the conflict with Riku to begin with.
And why shouldn't it? See what happened as soon as her Heart was out of his Body? (and, well, his too, but meh)
Kairi was left behind and he went after Riku. Hell, he told her bluntly she was a nuisance and ran off after Riku.
Then, when he had the chance to go back home, to return to his restored world, when he had the chance to rest -
Sorry, Kairi, gotta go, but (going by the manga for what it's worth) I promise I'll bring Riku back to you.
Mmhm. And Riku just told you to look after her.
And what did Sora do? Walk right into a trap because he was certain Riku'd be there. It later changed into Namine but hey - the main SoNami memory is the one of the Promise during the Meteor shower.
1) canNOT be a Kairi Memory due to the timing - she just reached the islands on the night of the meteor shower.
2) Repliku shared the Memory. Namely - both Riku and Sora had that Memory.
So... SoNami is based on SoRiku. Egads.
And of course, KH2. Sora knowing instinctively it was Riku all along whereas even Kairi needed Namine to tell her that. His obsession with the guy. Breaking his reunion with Kairi for the bastard who wanted to kill them all because, chances were - he felt it was Riku even with his eyes open. Of course, the breaking down into a helpless ball of sobs and hiccups and then becoming more energetic than he's been through the entire game. And then agreeing to become the Darkness with Riku.
We also have the whole BFF talk on the beach and even the post-credits scene before Kairi acts the plot device and runs in with the letter. About the closest that came to this, at least in the KH1-CoM-KH2 run, was the SoNami conversations but these two were riddled with plot implications.
SoRiku are the only ones who actually, deep into the game, at the freaking end of it, stopped, turned to each other, and just had a Heart to Heart. No forced comforting, no smiling otherwise the Gummi Ship'll run out of fuel, no "Ki-" "I'll save you!", no nothing. Just pure, honest to god bonding that ended in a form of communication I personally find to be one of the most intimate around -
Comfortable silence.
Who else in the freaking series had that, least of all only in groups of two?
Now I just need someone to point me at those mystery novel bits I heard so much about that had Sora and Riku hugging each other and I can die a happy, happy fangirl.
And why Bi?
Because SoRiku reflects on Rion and SoNami, duh xD
So yeah. Debatable relationship values with Kairi + painfully established obsessions with each other + fun statistics = I wouldn't be surprised if Sora and Riku are KH's Gundam Wing's Duo and Heero, waiting until Nomura'll laugh and nod when asked about their relationship.