Hi all - I've just finished Riku's story in Re:COM and am preparing to move on to KH2. I've played all of games in the series except for DDD (waiting for 2.8!), and 75% of KH2 before, so I'm familiar with most of the series lore.
1. Why does Riku decide to return to Castle Oblivion, leave Mickey behind, don the blindfold and work for DiZ? The end credits scenes aren't very clear; they show him doing that, but not why. 358/2 Days adds some context, and the prologue of KH2 a bit more, but I can't help feeling like I've missed something.
Nomura unfortunately set up Riku's storyline between CoM and KH2 (possibly including Riku's activities during 2) with the intent that it might one day be turned into a future game. He revealed all his future plot hooks during a post-KH2 interview and the Riku plot never got a game of its own. As a result, there aren't very solid explanations for the whys of Riku's actions during this period. Presumably he and Mickey split up to investigate or combat the Organization in some manner.
As for the blindfold, Mickey implies in KH2 that Riku needed the blindfold to contain the spirit of Ansem inside of him, saying that "His eyes couldn't lie." What that means, I... I don't know. I have Had Words with this particular plot point in the past.
I think it might be fair to assume that Riku did meet up with everyone in Maleficent's confederacy - Hades, Jafar (and presumably Iago), Ursula, Oogie Boogie, Maleficent herself - and we can't honestly say how long he interacted with them. Did he fight them? No, but I don't know if that's as important as it might seem - after all, Sora didn't deliberately give Monstro indigestion, Alice never tricked the Queen of Hearts, and other CoM plot irregularities. Since Riku kidnapped Jasmine in KH1, it's probably not unfair to assume he saw or even watched the boss fight with Genie Jafar as well.
As for the Heartless, Riku was of course there with you on the Parasite Cage, and if he didn't catch sight of the Darkside at Destiny Islands, he sure as heck saw it at the Door to Darkness in KH1! That means the only CoM bosses that Riku didn't actually encounter are the Guard Armour and the Trickmaster. Yes, it is a plot hole that he fights them despite never actually seeing them, but the problem's not as bad as it might initially seem.
Note that Riku doesn't encounter Cloud, while we're at it, so there's at least one case where the writers realize Riku didn't see something and didn't have him fight it in exchange... though that too could be a gameplay matter, since it would have broken with Riku's gameplay formula. Hrm, I wonder which it was?
While I'm perfectly comfortable with the game having this plot hole, if we really wanted to, I suppose we could try to fill it in. I'd just make up something about Maleficent showing Riku the fights as they occurred. Why not, right? Or maybe we could blame Castle Oblivion, saying it picked up the memories from Sora and plopped them down for Riku.
Thanks for the detailed explanation on both points! I guess point 1 is just one of those scenarios where we have to fill in the blanks of what went on between games, which is fair enough. KH is generally like that anyway.
Your explanation for point 2 makes sense, of course. There are a number of ways that Riku could have observed all of the fights that Sora had with the villains and Heartless. This fits with the implied timescale of KH1 - given that Maleficent provides him with a bedroom, he may have spent at least a few days in Hollow Bastion where he'd have plenty of opportunities to meet the villains. And your point about Sora's experiences in Castle Oblivion not exactly matching up with his memories is fair, too - if we discount NaminÃ©'s interference (in a few cases where she'd have no reason to mess with his memories).
Thinking about it, I can see how Nomura's plan for a Riku-focused side game might have instead become Roxas's story and 358/2 Days. Roxas spends a lot of time in a castle, surrounded by villains, and ends up questioning his role in the Organization. It's not hard to envisage a game similar to 385/2 Days in structure, but instead covering Riku's perspective during KH1.
I assumed that he doesn't meet Cloud because of the darkness in his heart only letting him recall dark beings, as Ansem claims. Cloud's misguided, but not a being of darkness.
Wow, yeah, I totally overthought that.
1) Honestly, that scene could've happened when DiZ and NaminÃ© were already at Twilight Town. The chambers are pretty much the same, if I'm not mistaken, and Ansem's reports kinda state that Riku appeared after he moved Sora in the mansion.
2) As Ansem(?) said during the gameplay: all that was left in Riku's heart were beings of Darkness. It doesn't matter how deep was the bond, if it's the only available. And Riku did meet all of them before they met their demise in KH1.
About Heartless bosses, there's no real proof he hasn't seen another Guard Armor or Trickmaster, KH1 showed boss Heartless aren't uniques at all, but instead of going there let us all remember Reverse Rebirth is kind of a "bonus" story: they didn't make new content when it comes to Disney Worlds, so of course it was just like Sora.
But yes, this makes the end-credits scene (where Riku clutches his chest and almost collapses, but presses onwards with Mickey following him) make a lot more sense; instead of going back to Castle Oblivion, Riku and Mickey travel onwards and go to Twilight Town, where Riku finds DiZ and NaminÃ© again. Mickey hangs around in Twilight Town while Riku is off kidnapping Roxas etc., then runs into Sora (once he awakens) and instructs him to go to Yen Sid, kicking off KH2 proper.