Okay, I think that when Riku left Castle Oblivion, he found the Destiny Place keyblade as a remnant from Aqua being there. But he couldn't actually use it's power, because it wasn't meant for him. I think he felt the power within the keyblade and to him, it resembled the power within Kairi's heart, so it was meant to be with her. I think Aqua and Kairi are the only two who are qualified to wield this keyblade because their hearts share similar power. And I think the only reason that Riku was able to hold onto this keyblade without it disappearing from is 1. He is qualified to wield a keyblade in general, but he cannot use the power of this specific keyblade, and 2. His heart shares a strong connection with Kairi's, and the only way it would get to her, is from him.
Thoughs?? (Don't flame plzzz!!)
Thoughs?? (Don't flame plzzz!!)