Street Fighter IV is a fighting game, so the story isn't necessarily an important part of the game. Regardless, each character has a unique back-story to them. Abel is a French mixed martial artist who has no idea of who he is and what his past is. Crimson Viper is a female American spy who enters the tournament to test other fighter's ability as well as to find out information. Rufus is an overweight Kung Fu fighter who seeks to beat Ken Masters and prove that he is America's best fighter. El Fuerte is a luchador who aspires to be the world's best fighter and cook. Seth is the boss character; he is the leader of SIN, and he wants to incorporate all fighting styles and become the ultimate being. Gouken, the older brother of Akuma and master of Ryu and Ken, returns to teach Ryu his final lesson.