Kaine is an Au Ra man who lost everything he had to Garleans. He was one of those adopted by Gaius but lost him too following the Sorrow of Werlyt. He hadn't had much contact with him beforehand but after he got the news of his siblings' deaths he ceased all communication. He fights as a commander on the Bozjan Southern Front because he thought that would be the single best opportunity to push back the Garleans. Even if his home is gone, he can fight to reclaim someone else's.

Kaine learned about being a Dark Knight from a brief trip to Ishgard and resonated with it so much he began training immediately. As he rose in the ranks he took to the field less often but whenever he does he takes on as many enemies as possible to protect the rest of his squadron. Comes off as extremely aggressive and rude when in reality he is just blunt and chooses not to get close to anyone. Has a soft spot for a certain healer Elezen who came to the force as a (pretty useless) trainee. When Kaine's around him he's unusually quiet in a calm way as opposed to an angry way.