In this game, Sonic and Eggman, by mistake, used the Chaos Emeralds to transport them to another planet; Earth. The Chaos Emeralds, however, have been scrambled around this world because of their mis-use. The race is on to find them, while Sonic meets new friends, and Eggman has a new, blue-colored, liquidy secret weapon called "Chaos".


This title was also re-released on the Gamecube under the title of "Sonic Adventure DX: Director's Cut". The new version had improved graphics, a Chao world added, (due to the Chao craze that was brought to the Sonic series) and unlockable Game Gear games were included after recieving a certain amount of emblems.

Name	Code	Function
Game Gear Unlockables (Gamecube edition only)	20 emblems: Game Gear version of STH1, 40 emblems: Sonic Drift, (first sonic racing game) 60 Emblems: Sonic Chaos, (GG-Only game) 80 Emblems: Sonic Spinball (GG edition) 100 emblems or 80 emblems with 20 Missions complete: Sonic Labyrinth, 110 Emblems: Game Gear version of STH2, 120 Emblems: GG version of Mean Bean Machine, 130 Emblems: Sonic Blast, 130 emblems and 20 missions: Sonic Drift 2, 130 Emblems: Sonic Triple Trouble, 130 Emblems and 40 Missions: Tails Sky Patrol, All 130 emblems and All missions complete: Tails' Adventure	After getting some emblems and defeating mission mode bit by bit, you unlock a Game Gear game.