I like the way that Auron is so awed at the sight of a sleeping woman. That seems remarkably sweet to me and also quite likely given the way Auron's life seems to have gone from what little can be pieced together from the game.
I find Yuna's intrusion on the scene to be amusing and her embarrassment is charming and I just know that is how she'd react to such a thing, with the sort of shock a child shows when her parents kiss.
I like the way that Auron becomes awkwardly businesslike in an attempt to cover up their liason and make it seem more innocent.
I like the way you compare Lulu and Yuna's magics and the different ways they feel and behave.
I like Lulu's prediction about Rikku and her reaction to the idea that Rikku might be jealous of her.
I really enjoy this focus on the relationship between Yuna and Lulu. I find the rapport you describe between them quite touching.
I rerally adore the implication that Yuna is asking Lulu to watch after Rikku not just for the reasons she speaks out loud, but also because she doesn't want Lulu to miss her too much. That's lovely and very like the selfless Yuna.
I'm glad that Yuna finally figured out what was going on between Lulu and Auron. I enjoy the gentle way she insinuates her knowledge and the fact that she wishes them well.
Lulu's thought that Yuna might send Auron and her questioning whether she could forgive that is insightful of you.
Nitpicking:
"Her white shoulder peeking out from under his coat hit Auron in the gut, and he wondered whether he should have been so quick to dismiss Wakka's and Tidus' ongoing debate whether the sorceress dressed that way to boost their morale or torment them." I would just change the wording of this to "the sight of her white shoulder . . ." just to clarify as currently it sort of seems like Lulu's shoulder physically hits Auron.
"In her mind's eye, Lulu could see the piers of the temple tinted pink by sunrise while Yuna clung to her hand and poured out her wish to become Summoner with shining eyes, or Lulu had admitted to herself and to her friend how she truly felt about Chappu one spare word at a time." I think I would separate the part about Lulu's confessions from the rest of the sentence because in the first bit I am thinking that Lulu is recalling a specific scene from her memory, but the second memory seems to contradict that. Also, keep modifiers close to their subject "Yuna clung to her hand and poured out her wish to become Summoner with shining eyes." Here you are saying that Yuna wants to become a shining-eyed Summoner, although what you mean to say is that Yuna's eyes are shining while she explains her wish.