Sonic Adventure 2 is a game in the Sonic the Hedgehog series. It is for the Dreamcast. It introduced two new characters, Rouge the Bat and Shadow the Hedgehog.
In Sonic Adventure 2, there are three story modes. They are the Hero story mode, the Dark story mode, and the Final story mode. The Hero story mode has Sonic the Hedgehog, Miles 'Tails' Prower, and Knuckles the Echidna. The Dark story mode has Shadow the Hedgehog, Dr. Eggman, and Rouge the Bat. The Final story mode has all of the characters. Sonic and Shadow can run the fastest and just go to the Goal Ring in their levels. Tails and Dr. Eggman fight enemies in mechs and go to the Goal Ring. Knuckles and Rouge search large areas for Emerald pieces.
Sonic Adventure 2 begins with Sonic being mistaken for Shadow and getting captured by the military. He escapes and comes across Shadow, who had stolen a Chaos Emerald before. Shadow uses it to teleport, and Sonic gets arrested. At the same time, Knuckles and Rouge fight over the Master Emerald. Dr. Eggman tries to steal it, but Knuckles breaks it into pieces so he can't. They start trying to find the pieces of the Master Emerald. Later, Tails comes to Prison Island to rescue Sonic, and saves Amy from Dr. Eggman. Amy frees SOnic from his cell, and he escapes from the island on a missile.