S.I.N.

S.I.N. is the weapons division of the criminal organization of Shadaloo. During Street Fighter IV, the leader of S.I.N. was Seth, who was likely also constructed as an S.I.N. weapons project. Many people believed at first that S.I.N. was really the remains of the fallen Shadaloo and not just a divison. During Street Fighter IV Guile, Chun-Li and Cammy are all sent to investigate its activities, including the construction of a dam which robs Dhalsim's village of water. Crimson Viper also spends years masquerading undercover as an S.I.N. operative, rising to become head of the Battle Suit development project. The World Tournament of Street Fighter IV is then used as the final test of the battle suit's capabilities. If successful, Viper hopes to be reassigned as head of the BLECE Project.

S.I.N.'s dam base is eventually destroyed when Vega activates its self-destruct. However, as Bison makes his return at the same time, it is unknown what the future has in store.