Kei Uzuki (有う月づき憬けい Uzuki Kei?), also known as “X” or “Slur” (×スラー Surā?), is the main antagonist of the Sakamoto

Yoichi Nagumo (南ナ雲グモ与ヨ市イチ Nagumo Yoichi?) is a major supporting character in Sakamoto Days and an old friend of Taro Sakamoto

Osaragi (大佛おさらぎ?) was one of the newest members of the Order, a group of the strongest assassins within the JAA.