1)
[You were just on a mission with Kuja and for some reason or another, you ended up saving the guy's bacon. Once the dust settles, he proceeds to head back without even acknowledging this fact]
2)
[You overheard Kuja negotiating a deal to sell some kind of weapon for someone from an Aware World. Once it's over he comes to you - no matter where you were positioned or even if you were hiding]
And what do you think you were doing, scurrying about like a rat? No... least a rat is quieter about spying on people.
3)
[he hovers before you with an infuriatingly smug grin on his face as orbs of magic start to appear]
You wish to fight me? Oh how brave you are! But you are merely the nameless soldier who dies in the first act.
4)
[Kuja is gazing at the false moon of the CO's grounds, and he believes he's alone]
Oh sorrowful moon who slowly climbs upon the star-draped steps - waning with the paleness of death... what omens do you see with the lifeless gaze?
[he chuckles]
admittedly not my best work, but better then the twittering of the groundlings.