Nothing, because he's not real.
Age: He's supposed to resemble an 18 year old.
Whenever he first popped into the game.
You can buy Zain's Drama CD here.
He's an NPC whose sole purpose is to dish out quests to players. However, he's advanced enough to serve as a potential love interest to Kazuha. A very... posessive love interest, that is.
Since he's just a computer program, he doesn't really understand a lot of human things, such as emotions.
I like Zain, he's such a cutie. I enjoy everything about him, from his design to his voice. The image above of him is probably my favourite CG in the entire game. I wasn't really sure how they were going to turn an NPC into a love interest at first, but they just made all of the NPCs really intelligent like they did in Sword Art Online.