You grew up in a small town on the coast of Japan. You were raised since birth as a ninja, in one of the few remaining ninja clans. One day, a pirate ship motored up and aimed machine guns at the dojo. They threatened to burn your village to the ground if you did not give them tribute. The town full of ninjas leapt in to action, and there was the most epic battle ever. In the end, though, the pirates lit the ninja village on fire. Which sucked. And so all the ninjas except you died, and only you survived, because you hid under a giant fallen slab of obsidian. And then the pirates captured you and made you a pirate.
You went around on their pirate ship for a while, plunderin' and lootin'. Quality stuff. Then one day, this giant sea monster totally attacked the ship. It was CRAZY. You randomly summoned a shiny sword to your hand and stabbed it. A lot. At the time, you were giving this weird guy in a brown cloak who called himself The Wanderer passage across the ocean (to California!) and he was like "Come with me, and I will teach you cool stuff." So you went with him and he took you to a school for magic and dropped you off. Good deal.
You quickly made friends with everyone, and hooked up with this hot chick named Aurora. Didn't last, but whatever. She was hot. Now you just kinda chill. Everyone is hecka impressed by the fact that you're both a pirate and a ninja. Yeah, you're badass. And basically the slacker Knight, but you know, whatever. You get along well with Isonade and Ironwood.