Sonic and pals are gearing up for some brawling action! Fight as one of nine characters including Sonic, Tails and Shadow! Knock 'em dead with special attacks and team-based assaults. Create and train fighting partner for 2-on-2 battles. Duke it out with your friends in 4 player battles. It is the second fighting game in the Sonic the Hedgehog series, the first being Sonic the Fighters. It is also the first Sonic fighting game to be on a handheld.

Many years ago, a sentient weapon was created by an ancient civilization. After being lost for millennia, the weapon, known as the Gizoid, was unearthed and researched by Professor Gerald Robotnik. It remained dormant for another half century before being discovered by, of all people, Gerald's grandson, Dr. Eggman. Frustrated at his inability to get the dormant Gizoid to work properly, Eggman dumped it at Emerald Beach where it was found once more, this time by Sonic the Hedgehog. Sonic names the Gizoid "Emerl", who gets wrapped up in the affairs of Sonic's friends, both allies and rivals. Through his encounters with Sonic, Tails, Knuckles, Amy, Cream, Gamma, Rouge, and Shadow, Emerl turns from a soulless robot into a fun-loving mech with personality traits from all of those he had met. But while the gang is having fun raising their new mechanical friend, there are those who recognize Emerl's true power. Now that Emerl is working again, Eggman has his eye on it, Rouge wants to turn it into a master thief, and Shadow feels that, despite Sonic's efforts to humanize him, Emerl is still a weapon of mass destruction.