The game begins with Sonic being given a tutorial by Tails on this new style of gameplay for him, as well as telling Sonic the latest news of Knuckles being kidnapped and the Chaos Emeralds as well. It's important to read each of these thoroughly in order to be fully prepared for the trials that lie ahead in the game. Afterward, go south down the path, grab the 4 Rings, then jump up onto the green path on the right side. Take the 4 rings here, then dash through the spiral loop to reach the other side.
Go north, take the 5 rings by the palm tree, then run into the Chao Egg to the right; a random Chao will hatch from this egg later when you hear a "cracking" sound. When this happens, open the status menu and enter the Chao Garden to see what you've got, and equip it. Go south now and talk to the man by the woodpile and speak to him for a Side Mission.
Side Mission: The Tired Old Woodsman
Reward: 50 XP, POW Candy. The woodsman needs help chopping his wood, so agree to help. Grab the axe to the southwest and tap on the logs' Interact icon three times to chop the wood for him. Go back and talk to him to receive your reward.
Head west now past the logs to find a box with a useful item in it, like POW Candy or a Health Seed. Continue west and look across the water to see an icon with a wing and a "II" on it; this means you need a character with the Fly II ability to get across. You'll have to come back later to reach this area when you have a character in your party who has this ability.
For now, go southeast to the dock and stand on the red button to pull a raft to you. Get on it and ride it south to the main island, where you'll encounter your first enemy, an Enraged Armadillo. You can't flee this battle, but don't worry, you will be hard-pressed to lose it. Just keep using regular attacks against the Armadillo until it's defeated.
Go south now and a Marauder will block the path with crates. Luckily, Amy Rose will join your party here, and her Piko Piko Hammer can be used to Smash through the crates. Continue down the path, picking up the 3 rings and the Chao Egg to the right, between the trees.
Continue south to face a Sentry Drone and an action sequence where you must chase after it while jumping over crates. If you hit a crate, you'll take 1- damage and slow down, so avoid them by tapping on either Amy or Sonic to jump over. Just attack the Drone when you catch it, then proceed south after defeating it. Take the 8 rings here around the box, then open it for some Prune Juice and a Health Seed. Attack the Enraged Armadillo and the Wasp Swarms.
If you're hurt, use the Health Seed you picked up to heal your HP, then head up the ramp to the west. Grab the 10 rings up here, and take on the Wild Boar here, killing it first before take on its companions to earn some XP, enough to level up. You can earn a point to level up your stats on a character (In this case Sonic). You can also use the five points you've earned to learn a POW move (In this case, you can choose between the Axe Kick, Whirlwind or Fastball). Now go north to find 3 more rings on the ledge, and note the red crates; you'll need a character with the Smash II ability to break them, so remember them for later.
Go southwest now and dash through the loop, grabbing the 6 rings and taking on the enemies at the end. Pick up the 8 rings here, then go east, take the 3 rings, and open the box for a Health Seed and POW Candy. Continue east until you reach your first boss, a Marauder Scout.
BOSS: Maruader Scout
HP: 70 • Weakest Against: Fire
The Maurader Scout will give you an opportunity to use your POW Moves, so use whatever you've been putting points into. The Maurader will use Statis Grenades that can put your party to sleep, so be sure to hit all the inputs when he uses it to avoid this fate! This boss can also sap away your HP, so use a Health Seed if necessary to stay alive. Keep using your POW Moves on the Scout until you run out of PP, then use regular attacks until it's defeated.
Follow the 8 rings here to Tails's Workshop and enter to replenish your HP & PP, and save your game. Speak to Tails about Knuckles to get him to join your party, then leave the workshop to face two Sentry Drones and a Swat Bot. Destroy the Sentry Drones first, then go after the Swat Bot; the Swat Bot will be revived with some HP at the end of the round if you destroy it before you destroy both Sentries. Either boost your attacks to account for the robot's armor, or use the Vulnerable status effect on it to lower its defense.
When all the robots are gone, go heal up and save your game again in Tails' Workshop, then head south down the road to find Rouge the Bat. As you talk to her, she'll be less than pleasant with Amy; your responses here affect your relationship with Amy later on, so choose your words wisely. Rouge joins you now and takes you to the G.U.N HQ, which ends the chapter.