Sanosuke Sagara is a lead character in the series. Sanosuke is a former member of the Sekihotai When the group is destroyed by the Meiji Government,, he becomes a fighter-for-hire to calm his anger by fighting. During his introduction in the series, he encounters the wanderer Kenshin,  who easily defeats him and is able to convince him to stop his mercenary work and instead start protecting people. After that encounter, Sanosuke becomes Kenshin's best friend as well as his partner in most of their fights.

(I do like Lex Lang's interpretation of the character, but a good guide for filling the role of Sanosuke is to sound like a cool and confident young adult)