Soulmate AU idea I've had for ages now so may as well talk about it at least a little bit. Features past Sonally full of longing and yearning, mostly platonic Sonadow with romantic undertones, and potential future Sonadally! Also music plays huge role in thsi AU coz the main inspiration be from the anime Given, specifically the song: Fuyu No Hanashi.
Starting with the soulmate part, we're going with the whole "red string of fate" vibe here, wherein every mobian is connected to their soulmate via a magical string tied to their pinky finger. Said strings are invisible to everyone else, meaning you can only see your own string, and even then the ability to see the string varies from person to person. However, when soulmates touch hands for the first time the string briefly becomes completely visible to everyone.
On that note, Shadow is a bit unique in that he has the ability to see all strings not just his own. Whether its due to the Black Arms or the nature of his creation he doesn't know, nor does he really know much about the whole soulmate thing in general as he was raised by humans who do not experience this phenomenon. And by the time he started learning more about it all, it was already too late. His string is already severed, a sure sign that his soulmate is already dead.
Worse still, between being blinded by grief and rage, he amnesia, and both his mind and memories being altered first by Gerald and then by Black Doom, he cannot remember when exactly it happened. He doesn't even know how he feels about it either. After all, how do you miss someone you never even knew existed?
And honestly? Shadow has a lot of big feelings that he doesn't fully understand or can put onto words. This is just adding to the list. And it's Rouge that encourages/forces him to find an outlet for his repressed emotions instead of just bottling them up and brooding into the sunset like his usually does. That outlet turns out to be music. He learns to play guitar and even joins a band. They've done a few small live shows, and talk about going pro tho never actually make any progress in that department. For the most part he keeps this part of his life separated, something thats just his.
Then one day he happens to run into Sonic just lazing about while holding onto a guitar with broken strings. Sonic has always been an enigma to Shadow for many reasons, least of which being the fact that he is the only mobian in the entire world that does not have a soulmate string.
The blue hedgehog has always been avoidant of the topic of Soulmates, his friends just assumed it was coz of Amy, but Shadow knows better. Even if he doesn't truly know the full reason... And despite himself, he cannot help but be intrigued. By the string's absence, that strange somber mood clinging to him that day, and by that damn broken guitar he's holding onto like a child with their security blanket.
He ends ups repairing the guitars strings which somehow leads to Sonic worming his way into Shadows band, his music, his life, and possibly even his heart! As it turns out they might just have a lot more in common than he'd either ever anticipated, with music being the connection that helps them channel and express their raw unspoken emotions.
