Harley Sutton is a non-combatant member of the 17th Military Arts Platoon within the academy city of Zuellni, where he serves as the group’s dedicated DITE mechanic. His primary responsibility is the maintenance, repair, and customization of the weapons used by his fellow platoon members, and nearly every weapon in the 17th platoon’s arsenal has been worked on by him. He takes great pleasure in adapting and fine-tuning these DITE, showcasing a deep passion and technical skill for his craft.

He has a longstanding relationship with the platoon’s captain, Nina Antalk, as they are childhood friends. As part of the 17th platoon, his colleagues include the sharpshooter Sharnid Elipton, the Psychokinesist Felli Loss, and the main combatant Layfon Alseif. Because his role is entirely supportive and technical, he does not participate in combat and therefore does not wear a battle uniform like the other members. Instead, he is typically dressed in a mechanic’s outfit consisting of a black t-shirt, a gray coverall with long sleeves tied around his waist, brown gloves, and a blue cap worn backward. He also has gray eyes and shoulder-length green hair tied into a braid.

As a non-combatant, he lacks notable combat abilities or Kei-based powers. His development is tied to his support role within the platoon, focusing on his contributions as an engineer and alchemist who ensures the team’s weapons function optimally during their battles against the Filth Monsters. His personality and motivations are largely centered on his work as a mechanic, and his story role is to provide the necessary technical support for the platoon’s military operations.