It's the year 2050. You were born in a world where every country was at war with each other. It was the Fourth World War and everything was at chaos. You were lucky to be born with parents who taught you how to survive in harsh conditions.
Your mother taught you to steal, a thief that can go around undetected. Your father taught you how to fight at close combat with swords. Not only that but you also became an expert at hand to hand combat.
You travel the world alone trying to survive. To get away from a simple battlefield is hard. When governments took notice of your talents they began to hire you to join their war. You agreed to every job on a certain condition: that is to never be a permanent fighter for them.
The world split into two enemies. The Military Powers and The Survey Corps. You of course work for neither of them. Right now you are allied with the Military. Only a few days ago was your life at stake. The Survey Corps also has its own assassin. His name is Levi Ackerman, and he was hired to get rid of you.