Okay, guys, I pulled out my volume 3 of the manga. Remeber inside that castle, when they were going in circles? The minute Syaoran picked up that pebble, to show they were going around in circles, Fai went Hyuu for the first time. The very first Hyuu.
Fai says: I don't feel like walking anymore.
And he uses his 'sense' on the wall. That shows that he used that hyuu to activate the 'sense'.
-2 Hyuu's in the battle with... what's her name. That witch. Later on, Kurogane asks: If you don't want to die, can't you atleast try to use your magic?
Fai responds with: No, sorry.
Does this mean Fai tried twice, but failed both times?
-In Volume 4, Fai goes Hyuuu after Kurogane knocks the gun out of that villager's hand in... Jade country. But there doesn't seem to be any sort of magic following it up. Maybe he was actually impressed this time?
-Another Jade country Hyuu after Syaoran and Sakura get pulled out of the water. (after that whole castle scene) Again, no magic seems to follow up, nor is there any reason why Fai would attempt to use magic. Maybe to cover up all the real Hyuu's, he's using them randomly too?
-In Outo, before Fai 'writes down' their names, I see a some sort of musical "Hmm?" (kinda hard to explain. But there's a musical note there.) Could it have anything to do with what Fai says later on? That magicians are really good at drawing? Later on, when he's drawing the sign for the Cat's eye, he's actually sorta singing...
-One thing I noticed is that in Outo, when Fai and Kurogane are fighting in front of the Clover bar, Fai doesn't attempt a Hyuu once. Did he realise they're in a game, and his power is useless there? During the battle with Seishiro, there was still no Hyuu. Only a quick mention of not wanting to use his magic. Hmmm....
-No Hyuu in the Shara/Shurano/whatever those countries are called saga... But then again, you hardly see Fai in that saga. It's mostly Kurogane battling.
-Fai goes Hyuu in the first race of Pfiffle country, after Syaoran avoids a sudden 'windstorm'. Not much magic affialated with it. I think he was just impressed.
Though a few pages later, Kurogane says: We just have to seize the feather and transport to another world before anyone can react.
Fai says: You never know, we might have to do that in the end.
Fortune telling, perhaps?
-A minor Hyuu when Fai and Kurogane are watching the news, and there's a big zoom on Kurogane's face.
-After Sakura wins the race, Fai goes Hyuu again.
Kurogane: I told you to quit saying that sound.
Fai: But I tried practicing in Yamano country and I couldn't do it. (What is Yamano country?...)
He swore not to use his magic, yet still practises whistling? How does that make sense?
-Strange though, that in LeCourt's central library, when Fai touches that wall, he doesn't go Hyuu.... Fai does however start Pyuu-ing when those strange dragonlike creatures attack. He says it sounds almost like a whistle, and continues doing it.
-After getting LeCourt's feather, and discovering the guard dog is waiting for them, Fai manages another pyuu. Another random pyuu as they escape... And another Pyuu after watching Fai's hat melt... A pyuu as the dog lunges towards them and then.... The REAL DEAL!
A nice double pyuu (most likely real whistling) as the magic appears.
Aaaand that took me about two hours. @_@
