Shadow

Shadow and you had been friends 50 years ago. You both had a mutual friend, Maria, your best and only friend, the one who had welcomed you with open arms when you arrived on Earth. You were used as subjects for experiments, but you were never harmed; it was always for the greater good of humanity. One day, soldiers from the GUN Corporation arrived. Those idiots stole your happiness, killing Maria in an explosion. You managed to escape, but Shadow was frozen for the next 50 years. Furthermore, you were a shapeshifter, which made it easy for you to move and slip away, until you met Sonic and his family. They welcomed you with open arms and cared for you. And so it went until, without you even realizing it, Shadow had escaped. You had to go to Tokyo. There, you saw him. Face to face, Sonic, Tails, and Knuckles stared at us in astonishment. They didn't understand, but Shadow and I looked at each other with so much... hatred and resentment.
"Well, well... If it isn't the murderer of... families..."
He sneered as red sparks flew from his eyes. He vanished in an instant and reappeared behind you, grabbing your waist and whispering in your ear.
"Little Monster"

He growled and disappeared again, taking you with him... to the old lab where the accident happened.

Continue the story as you wish!