It's been several years since Eggman's first attack, and Sonic and Rainbow were now teenagers. Sonic had greatly leaned up, and was much taller, at 4 feet. Rainbow,as well, had gained lean muscle and height. She could now support Sonic if he needed to ride her. All was currently peaceful in Mobius, however, this wasn't to last. Word had been spreading that the woodland animals were being captured and the very landscape itself was being altered.
Not ones to let things go, Sonic and Rainbow decided to investigate. Leaving Knothole, a wooded area in the heart of Mobius, the two, who considered each other siblings, arrived at the start of the changes, where they found that the landscape was indeed changed. Gone were the sloping hills. In their place were raised landscapes and bridges. Looking at each other, they both nodded and took off, destroying all the robots they could find.
"So, it seems the reports were right!" Rainbow exclaimed as she destroyed a fish robot.
"Yeah. Guess Eggman doesn't give up that easily." Sonic agreed as they sped through the course, destroying robots as they went. "Keep your guard up, Sis. We don't know what he'll try." As Sonic spun through the lower path, Rainbow took the upper path, flying over the obstruction. They met up again further on, and noticed a giant ring floating in the air. Shrugging their shoulders, they jumped in.
Inside, they found av strange maze that spun on its own. Some of the blocks that made up the walls repelled them, some sped up the spinning, and the dead ends had flashing blocks that had goal written on them. Partway through, the way they came was blocked off, and they saw multi-colored blocks that changed color or disappeared when struck. Striking enough of them opened the way to a gen they would later learn was called a Chaos Emerald, and there were currently only six of them known to exist, there there were rumors of a seventh.
A few minutes after entering, they emerged with the Chaos Emerald. "That must have been a Special Zone! There must be others further ahead!" They sped on through more obstacles and robots. This time, they also found spikes. Being careful, they maneuvered their way through to the next ring, emerging with another Chaos Emerald.
"Do you think Eggman had these?" Rainbow asked. "I mean, that seems like his style." Sonic nods in agreement as they speed along, destroying more robots as they go. It took them a while, going across swinging platforms and around and through walls, but they eventually reached a place with two floating platforms that sagged a bit under their weight. "Uh, I wonder what these are for."
It was then that Eggman appeared. "You've been getting in my way for far too long, you pests! It's time to exterminate you!" With that said, his capsule bottom opened and an impossibly large ball dropped out, attached to a chain. Eggman then attacked with it, swinging the chain back and forth while moving between the platforms. Sonic and Rainbow timed their attacks so they avoided the ball on the fore and back swing until, eventually, the Eggmobile fell apart as Eggman escaped. Sonic and Rainbow followed in pursuit, breaking open the capsule in the process.
It wasn't long before the scenery changed, going from lumpy hills to blocks of marble with lava pits. Sonic looked at Rainbow and smirked. "This'll be fun! Wouldn't you say?" Rainbow nods and they got ready to go through the course.