(This story takes place in the Sonic Movie universe, and as such may have spoilers. However, due to an ongoing story and numerous similar storylines, I will likely take multiple creative liberties+influence from other Sonic media.)
This story takes place just a few years after the release of Shadow the Hedgehog. Sonic, Tails, Knuckles, and now Shadow are all trusted members of G.U.N. They're usually only called in for issues pertaining to them, supernatural occurrences, or things of the like, but this time there's a different reason.
"We've found something that's in orbit of our planet, and it's man-made. We believe it to be a piece of Robotnik Tech."
. . .
"Shadow, you know her? Who is that? She looks like the inverted version of you..."
As a young girl with her whole life ahead of you, being forced to marry and be nothing more than a housewife was never part of your plans. With the gift of a beautiful voice, and the passion to be a hero you dreamed to have more than just a simple life. Though already engaged to a young grasshopper by the name of Yirel, you both have moved to The City of Tears to fulfill his dreams. When it all seems so bleak, you catch wind of red tents appearing on the other end of the city that links to an old tale long before your time. When you start taking interest in the tents, your life begins to slowly change. Your dreams to be a hero are not yet lost as you start to see yourself as part of a bigger picture. Dreams are dangerous, but maybe you could change that.