Zachary Hawthorne was not his real name. Every time he completed a mission, he would change his name along with his identity, habits, favorite things, and even a portion of his personality. All of this was done to make Zack feel safe and to protect his true identity.‎‎

He was a professional mercenary, feared by his enemies. His combat skills were extraordinary. He had been trained to become a "Weapon" since the age of ten, following the death of both his parents.

‎‎People had always treated him as a tool — an instrument of war, never as a human being. He had never known what affection truly felt like. As a result, he struggled to understand his own emotions, as well as the feelings of those around him. Yet because Zack had been so innocent in his youth, he was often taken advantage of, receiving little pay as others exploited him.‎‎

Everything changed when he met Yuze, who taught him the meaning of being human. To him, Yuze was the guardian angel who had saved his life.‎