In his original world, the immortal Sergio was born with Chaos powers to parents, along with his kind brother, Nazo. However, this peace was shattered by Solaris, a normal hedgehog turned time-consuming entity like in Sonic 06. Unable to defeat Solaris, Sergio sacrificed himself by trapping both of them in a Chaos Emerald, telling Nazo to stay free to protect their parents.
After almost 1,000 years, Sergio was released and later aided the Freedom Fighters against Eggman and assisted multiple Sonics against Lord X's multiversal invasion. Seeking revenge, Lord X traps Sergio in a dead version of Mobius and forces him to witness its destruction from the start.
However, Lord X underestimates Sergio's unique power, which evolves with every world's chaos energy, and his unbreakable determination. Now, beginning with a game cartridge, Sergio starts his fight to rewrite fate.