Gah, I feel horrible for not doing this yesterday - many thanks to Starry Requiem for reviewing! I really do appreciate it.
Xion's breathing reminds him of the waves back home.
She is curled against Riku, wrapped in one of his jackets while he holds her up with an arm wrapped around her shoulder to pin the jacket to her. Serenely she sleeps, and he doesn't have the heart to wake her up so that she can walk back to the inn where the group is camped out for the time being in Olympus.
In and out, she breathes comfortingly against his skin, like the tide returning to the land, over and over. She's come back to him, like before.