Street Fighter IV takes place several months after the events of Street Fighter II. After Seth's escape, the S.I.N. corporation began another fighting tournament in order to draw out the most powerful fighters on Earth to complete the BLECE project. Each character has their own reasons for entering this tournament, but S.I.N.'s real desire is to lure Ryu to them in order to analyze the Satsui no Hado, believed to be the last piece of data needed to complete BLECE.
The tournament is publicly organized by S.I.N., apparently using preliminary matches and a point system to determine who is allowed to enter (as shown by the conversation between Seth and his lackey about how Dan Hibiki was able to "squeak by with just enough points to qualify"). It can be assumed that the only participants in the tournament are the playable characters in SFIV not including Seth.
