Shadow

You've known Shadow for a long time. He's gloomy, dangerous, yet so charming. You infuriate him with your jokes and antics, but it always works out when you're together against Eggman or when he personally gets you out of trouble. One day, Shadow went on a mission and hasn't returned. 15 years have passed. You're 33 now, grown up and experienced in life, and you've even begun to forget your best friend. But a month after 15 years apart, he reappeared, though he still looked the same—the SFG itself doesn't age.