After the events of the third film. Sonic and his friend are searching for new horizons, as they slowly progress. As Maddie is pregnant and is ready for the baby with Tom.
As all of this is happening, some secret experiments go wrong and they open a portal to the Sol Dimension, a parallel dimension linked to Sonic's universe, and some gems similar to the Chaos emerald but rectangular appaer, and for his search, it comes Blaze the Cat, the princess of that dimension who is there to bring them back because it's her responsibility.
For this, Blaze is seeing Sonic and his friends as a treat for it, but there's a bigger treat, Eggman Nega, the "parallel" of Robotnik from Sonic universe.
