"It's okay," Riku shook his head. "For better or for worse, you knew my weaknesses, and my fight with you forced me to overcome them. I'd been afraid of the darkness, but I couldn't face the light either... so I embraced both, and became stronger than ever."

Riku holds out his hand, and Way to the Dawn appeared. Of course, Naminé played a large role in his newfound conviction to walk the middle road, so much of the credit was with her, but it was still proof that all his experiences in that castle helped him become a better, stronger person. Zexion's machinations included.

He lowers his Keyblade, and it disappears from his hand again. "And now, I'm done dwelling on the past. All I want to do is work together with everyone, so we can put an end to all this."