"He's coping." Which was more than Sora was doing.
"Everyone had to deal with pain in their own way. Better to feel it, than bottle it up."
And if Sora thought no one was worried about him, he was SO wrong. He's the person everyone is most worried about, except maybe Hayner, but that's just because he has Rachel to worry about.
"Tidus," Riku said, opening his door, "Sora's staying with me tonight, okay?" It wasn't like they'd DO anything with him there, so really, it SHOULD be fine.