Sora knew he didn't want to, but that was exactly why he had to right now. He knew when to baby Riku and when to help him along by now. Or at least he was learning as fast as he could.
The Prince waited for Riku to decide what he was doing. He'd like him to come sit by him, but he let him go off as he wanted, then waited a moment as he came back.
"Alright. Go ahead." He told Corin. So he could open it and read it, hand it off to Sora, and then Riku would see that there's nothing wrong at all.