Normally Riku would fire back with some quip in regards to Sora's certainty, but instead remained quiet. He wanted Sora to be right.

Riku turned it over before a slight smile crossed his features. "It looks too fresh to be a dinosaur tooth." He held it up for Sora to see again. "But it looks like one, doesn't it?" It did look very similar to stuff in text books they'd seen when they were younger. But no world they'd gone to had Dinosaurs still alive or anything that strange... Right?

There was no hesitation when Riku took it. He held it in cupped hands as if it were fragile, though given the drop off the tree it clearly wasn't. Slowly he pressed it to his chest, his face a mixture of pain, longing and confusion. "...Why is this so precious to me?" He closed his eyes a moment, trying to remember, but he clutched the charm in a very caring way.

"Well, are you going to find out?" He was still clutching that charm like he was holding his own heart, but his eyes were very much focused on Sora.