Nine was a man of reasonable height with fair skin and thin, rectangular gray eyes and white pupils. He also had white hair that reaches just past his shoulders, worn swept back away from his face. In the past, Nine wore black shoes, black pants, and a tattered white jacket.
His most defining feature was the large black mask that covers him from his chest to just above his nose, four extra pieces winding around the exposed skin of his face and around his head. Four darker plates cover each side of his neck, lined with dark purple, and he had what appears to be something similar to the flat muzzle of a gas mask over his mouth that’s decorated with seven gray studs, as well as a large purple and black cylinder protruding from each of his shoulder blades. Below this, he wore a full-body suit of a similar design, with plates of black covering his entire body, leaving only his fingers exposed, and, over this, a blazer and dress pants of a pale lilac color. He also wore black boots.
Nine was a frigid person, unfazed by most situations. He did not attack anyone unless provoked, and used his Quirks to ward attacks. If pushed enough, however, he was prone to violent fits of rage. He would also completely abandon any restraint in those moments, demonstrated by him attempting to choke Mahoro Shimano to death in order to force Katsuma Shimano into getting his Quirk taken. Despite his overwhelming strength, Nine was very humble, and greatly valued those who demonstrated impressive strength by his standard, let it be an ally or enemy.
Nine believed that a truly superhuman society should be one where hierarchy is determined by one’s strength, making heroes and villains irrelevant. With the ideal that might makes right, Nine was prepared to undergo whatever experimentation was necessary to increase his own power.
Nine’s philosophy and motivations were not just for his own sake, but also for his teammates Slice, Mummy, and Chimera. He sympathized with their lives of oppression due to his own similar past and wanted to enact their collective desire to build an ideal world for all four of them, as shown when he talked to Kyudai Garaki about his goal as he thought of his friends while referring to “their” ideal world.