*blink blink* Sheesh... I'm gone to work for 13hrs and I miss all the 'fun'. (BTW Emiko, Jeannette, if I could give out cookies I would! Lovely responses!)
Any way! I am also of the belief that Fay's personality won't change that much. What I could see is a possible depression, or self loathing happening for a while until Kurogane (or maybe Fay in a sudden show of personal growth) snaps him out of it. I can see him getting lost in space, and the smiles being slightly more forced, but once again, the time spent on this would probably be very limited. In the grand scheme of the Tsubasa world, the current Fay problem is merely a subplot and should end with in a the next few chapters or so.
Anne Rice seems to have largely shaped the way the Western Vampire is seen. Rather than Ghoulish figures we see in early films, Such as the Germany release of the 1922 film “Nosferate: eine Symphonie des Grauens”, in which Max Schreck brought life to Stoker's character for the first time, in a rather frightening portrayal, then the character was later given a more sophisticated upgrade in 1931 film “Dracula” But was still very frightening to see.
Rice gave vampires more depth, in Interview with the Vampire and it escalated from there. I'm sure we're going to see something along the lines of a more Ricean Vampire lore (which is quite similar to current Anime/manga types) Where 'feeding' is seen as a highly sexual experience (Thought his seems to be true in most vampire myths) Considering the most common places to bite tend to be more on the.. ummm 'sensitive' side. The wrist being the most impersonal... but even then a bite there can send it's victim on a delirious rush of pleasure. (I can hope for this right? *happy fangirl land)
Though there is a running theme with most vampire stories, it is how they deal with immortality, and the loneliness that comes with it. I'm not sure how they will handle this with Fay, considering he's only half vampire and bound to Kurogane. Is it possible that Fay will stop aging and look roughly early to mid 20's for the rest of his life (whenever Kurogane dies)? Or because he's only a half blood would he still age like a normal human? Those are the questions I am seriously curious about. Though it's hard to tell if CLAMP will even dive into such detail, and that line of thought might be left to the hands of fanfiction authors.
And in final note... I am also HIGHLY curious to know how Ashura is going to respond to Fay if those two ever meet face to face again.
Fay: Ashuraou....
Ashura: WTF? O_O
Hehe...