Enigma
The silver-haired Coordinator doesn't really understand what his rival/friend sees in the tomboy representative of Orb, when he just learned of their relationship.
Yzak Joule remembered noting that there are lots of Coordinators who were definitely prettier and more feminine, than the Natural, like the pink-haired songstress, when he saw Attha in person. Seriously, how on earth Athrun preferred to be with Attha rather than Lacus was beyond him. So, maybe Athrun doesn't really love Lacus romantically, but still, the blue-haired coordinator could have chosen someone better.
-shshshsh-
Yzak doesn't hate Naturals anymore, but he is still having a hard time accepting that his friends are in love with Naturals. He could somehow understand Dearka, since his friend is mostly a crazy person…but Athrun?
He thought highly of him, not that he would openly admit it. Athrun was intelligent and was more sensible than Dearka, so what happened to him?
What was so great about that blonde? He was somehow intrigued.
-shshshsh-
"Thank you, for saving my life once." That was one of the first things she said when they actually had the chance to talk alone. Not that he was keen on speaking with her.
He shrugged, "It seemed to be the right thing to do at that time."
-shshshsh-
Little by little, through meetings and other occasions organized by their mutual friends, or parties organized by world leaders, he learned more about her. Of course, he read some articles, watched some news about her, but you can't trust everything that the media conveys.
She was hot-tempered just like him and is definitely not afraid to speak her mind. She was very much loyal to her country and would always think of what's best for everyone. Cagalli was one of the most caring and unselfish person he met.
They eventually became friends, which was quite a surprise for him. It was a pleasant surprise, though.
-shshshsh-
Cagalli Yula Attha was the most beautiful person he had known, he realized. And he then understood what Athrun Zala saw in her.
Her warmth, her ability to make a person laugh…
Her determination when she is fighting for something or attaining her goals…
Her way of making people feel special and loved…
had also made him fall in love with her.
-shshshsh-
He could only love her secretly. Maybe that's one of the secrets that he's going to bring to his grave.
It was already bad enough that he had fallen in love with a Natural, who is the twin of the person who once placed a scar on his face.
But what's worse is that her heart already belongs to Athrun.
Yzak sometimes feel a bit resentful towards Athrun… and he usually wonders what Cagalli sees in the blue-haired Coordinator, that he does not have.
But, since Cagalli was happy with Athrun, he was trying damn hard to be happy as well. Athrun really needed to make sure that he would not hurt Cagalli, because he was sure that not only Kira would wring Athrun's neck.
-shshshsh-
AN: I can't remember if Yzak & Cagalli have met in person in the anime (sheepish grin).,, And I call myself a Cagalli-Yzak fan (LOL)