Saitō Hajime is the former captain of the third unit of the Shinsengumi, a hitokiri, and currently a special agent for the Meiji Government's Department of Internal Affairs. Having a long-standing rivalry with Himura Kenshin since their days on opposite sides of the Bakumatsu, Saitō nevertheless holds a begrudging respect for the rurouni and has come to his aid on assignment more than once, acting as a ruthless ally and the voice of cynical reason in the Kenshin-gumi's major battles.