For being our leading man, we really don't know all that much about Ky. Sure we get to hear passages upon passages about the dreamy uniqueness of his eyes (dark blue, deep, and soulful, in case you somehow missed the 382 times this is mentioned); and sure we know that he's an Aberration from the Outer Provinces, that his parents were killed when he was young, and that he can draw and write real words (in cursive, no less)—but Ky suffers from First Book in a Series Love Interest Syndrome, so if we had to pick one word to define him it would be mysterious.
His main purpose in this book is to serve as the catalyst for Cassia's transformation. He opens her eyes to a world beyond what she's come to expect for herself, and to what Society's really all about. His importance in Matched is less about who he is, and more about how he makes Cassia feel. He's a tool more than a multidimensional character at this point, though a drool-worthy tool at that.
There are hints that there's more to our blue-eyed mystery dreamboat, though. For instance, he's smart enough to know how to blend in:
Ky can play this game. He can play all of their games, including the one in front of him that he just lost. He knows exactly how to play, and that's why he loses every time. (20.100)
Yup—looks like Ky not only understands the rules of the game he's playing, but also the rules of Society's game. In other words, he's at least a couple steps ahead of Cassia when it comes to understanding how the world they live in works.
Despite years of playing it safe to fly under the radar, Cassia brings something out in Ky that inspires him to take risks again. She says:
I think of him risking everything each time he slips one napkin into his pocket. All these years he's been so careful, but now he's willing to take a chance. Because he's found someone who wants to know. Someone he wants to tell. (19.60)
Our fingers are officially crossed that Cassia finds Ky and we get to hear more of his story. While we're all for eye candy, we suspect that Ky is a pretty interesting character in his own right—so though Society might not be curious about him, we certainly are.