The result of genetic expeimentation by a highly scientific country, Rai has always had immense physical strength, increased reflexes, and insane durability. He has never had difficulty in a fight, and cares little about academics. Never losing at anything, Rai has an air of arrogance around him, and is endlessly teasing those he likes, and insulting those he dislikes. He is one of the most powerful individuals in his country, and is sought after by many factions for his strength. 
Rai is a very loud and brash young man. He has been raised from birth to do one thing, fight. The ones who created him wanted to create the most powerful soldier in the world who could change the very tide of a war, but they never expected one thing, Rai's personality. Rai holds his own morals very dearly, to the point where he will thoughtlessly break a law if he believes to be in the right. Though due to his youthful zeal, he can sometimes refuse to follow the rules only to rebel. Rai loves to fight, he loves the thrill of it, and while anyone he fights ends up injured, he refuses to kill anyone. 
Rai's voice should be a bit youthful, since he is only 17. Besides the above lines, we also have an audition script, which you can get here: http://studio-freedom.deviantart.com/journal/Rai-and-Alistair-audition-script-610215127