Although appearing middle-aged, Kylie was, chronologically, a young man with black eyes and black hair. Kylie's consistent doping took away his youthful appearance, leaving him with gray hair and rhytides. He wore a standard Dark Squad uniform that predominantly consisted of black attire; a shirt with long sleeves, a pair of pants and shoes, leather arm guards covering his outer forearms and a white belt that holstered two short swords on each side, with kusazuri behind his waist.
Kylie presented himself as a cheerful and determined person with an uplifting spirit, especially around his teammates. He always chose to see the bright side of things, as not to focus on the negative. Frequent substance abuse left him with mood swings, though he appeared to have control over them. Kylie held unquestionable loyalty and pride for the Empire and considered defectors to be better off dead than to have them betray their trust. This might be one of the reasons why he despised the Elite Seven. The two sisters were one of his closest friends. He spoke highly of the two and addressed them with the suffix "cchi", even after Akame's desertion. However, his respect for the elder sister withered away after she abandoned the Empire.
Kylie was one of the children taken by the Empire to be transformed into assassins. However, he did not possess the characteristics to be one of the Elite Seven so he resorted to the use of different drugs to enhance his physical abilities. Frequent doping robbed him of his youthful appearance, for which he held Akame to be responsible. At some point, when the remaining original surviving members of Group of Terror are transferred into Elite Seven after the raid on the tomb, Kylie was assigned by the Unknown leader as leader of the new Group of Terror.