With intelligence, strength, and intuitions superior to his brother's, 15-year-old Yuki Aiba has no need for his older brother Kouji, Kouji's friends or Kouji's patronizing - indeed, fights are inevitable whenever the Aiba boys meet face-to-face. A lone wolf, it is hard for him to live with others. Very athletic, and with outstanding piloting skills, Yuki ranks at the top of the Level 2 piloting class. Possibly the best pilot on the Ryvius after the Zwei, Yuki is one of the five main operators for the Vital Guarder, a giant mecha that acts as the primary weapon of the Ryvius. He shows himself to be the most skilled operator on a number of occasions. Aside from the above, he also has an interest in girls; he broke off with his first girlfriend, brunette Erina Rigby, aboard the Liebe Delta just prior to the station's collapse. His current girlfriend is Cullen Lucciora, a piloting classmate and fellow Vital Guarder main operator.