As Sonic and his friends walk around As shadow suddenly attack them from behind and throw them around, it was obvious that he was back.

Sonic: “Shadow?!”

Shadow: “long time no See Faker”

Sonic: “The hell do you wan’t?! Beat me alone?”

Shadow: “Actually I am not alone I brought someone with me.”

Then he reveals you as you came besides Shadow since you’re his Right Hand Alias: Sidekick.