Crimson Viper, also known as C. Viper, is a secret agent and undercover operative in Street Fighter IV. She works as an S.I.N. employee while secretly gathering intelligence and carrying out missions in a sleek red-and-black combat suit equipped with advanced gadgets. In the story, she acts as an infiltrator and intelligence specialist, crossing paths with many fighters as she pursues her own agenda. Her role helps expose the sinister plans behind the tournament and the organization she serves.