The only surviving grandchild of Professor Russell, Carl has lived in HERZ for the majority of his life. His grandfather took him in and gave him a home after a devastating DEDT attack took the lives of both his mother and father.
As a young adult, Carl trained to become a soldier to defend against such attacks. A talented recruit, he mastered the R.O.C. training regiment in record time. However, during this period, Professor Russell mysteriously disappeared. Wracked with guilt at having not been around to protect his grandfather, Carl joined the elite R.O.C. team in an effort to save him.
Several years ago, Burton's parents were killed in a DEDT attack that targeted the founder of HERZ: Burton's father. The attack was brutal, but Burton's sister was declared missing. Her body was not recovered from the scene of devastation. Burton joined the military shortly afterwards, hoping to avenge his family and find his younger sister.
Years have passed, but Burton continues his search. War weighs heavily on him, but he finds solace in being the big brother of the entire team. He watches over everyone with care and bravely takes the brunt of every attack.
Her R.O.C. squad nicknamed her "Lil' Miss Headshot" because there is no better sniper in the military. Her father, General Hugh, suspects Carl of being somehow involved in Professor Russell's sudden disappearance and has sent Marie into the elite unit to watch and report on him.
While Marie obeys orders and dutifully reports Carl's activities and movements, their work together has built trust between them. She has determined that she will support Carl, despite her father's misgivings.
Ai's childhood was a struggle against her perfect sister, Maii, to gain their parents' attention. Unlike Ai, Maii excelled at everything she tried, from gymnastics to ballet to sharpshooting. Maii later became a war hero in the R.O.C. Ai's love and jealousy grew until an incurable illness struck Maii down behind enemy lines.
Hoping to both surpass her sister's memory and alleviate her own guilt, Ai became determined to join the R.O.C. herself. She strives to both follow in Maii's footsteps and outperform her at every opportunity. Quick and nimble, Ai complements the team well as a forward scout.