Shouldn't Riku be the real holder of the Kingdom Key'D? Like, he was once the bearer Kingdom Key and he lost it first in Destiny Islands because he was sinking into the darkness and later because of the light of Sora's heart, so if he was once fit to the Kingdom Key and he lost it because of his darkness so this doesn't make him the best choice for Kingdom Key'D (the Kingdom Key counterpart of the Realm of Darkness). It could happen in the future that Mickey was just the "delivery boy" of Kingdom Key'D since he also bears the Star Seeker? Riku is also known in the series as the "Hero of the Darkness" and the "Hero of the Light" (Sora) uses the keyblade of the Realm of Light and it would make sense if they were the "Kingdom Key duo" since they already are a duo. What do you guys think? 

Mickey has spent longer in the dark realm than Riku so it makes sense he has it instead imo. 

nah, plus i prefer him with the way of dawn keyblade

I think the Kingdom Key-D plays by different rules. Whoever finds it, gets to use it.

The mouse beat him to it.

I think the Kingdom Key-D plays by different rules. Whoever finds it, gets to use it.

Yeah! It's kinda weird that we have this multi-bearer story with the Kingdom Key and we don't even know why Mickey has the Kingdom Key'D or how he get it  

Actually, Sora should've had Kingdom Key D in KH1 while Riku should've had the normal Kingdom Key.

I think Aqua's been there a while...

The only known difference between RoD and RoL Keyblades is the place they hail from. I take it that KKD choose Mickey for the same reasons that most Keyblades chose their masters, primarily because they have a strong heart. I think KKD was always meant for Mickey, it's just that since they resided in two different realms KKD couldn't reach Mickey so Mickey went to it instead.