Earlier. It was between the OP of the first episode and the beginning of the episode, if I remember correctly. It's when Misuzu said she spent the afternoon sitting next to the sleeping Yukito, watching the kids play on the beach, and wishing that he would wake up and they could play together.
As for Kanna wanting to go to the beach - that was in one of the Summer Special episodes wasn't it? I'm planning on watching AIR again soon, after my exams are over in two weeks. And the Summer Special is almost as sad in it's own way as the final two episodes of the AIR arc - if only for the horrible irony of Kanna's final words to the gorgeous little bunny she adopts.
I miss waiting until 3am to watch the latest episode of AIR. Strange, but true.
-Andiyar