A2 was part of the experimental YoRHa squadron deployed on the Pearl Harbor Descent Mission during the 14th Machine War. A2 ended up being the last survivor of the YoRHa squadron after the mission, causing her to be declared a traitor and deserter by YoRHa Command due to the secrecy of the prototype YoRHa line. A2 then survives alone, driven on by vengeance to defeat any machines and YoRHa units she comes upon on the way. She has a fiery personality but secretly kind and compassionate