Throughout each act, you'll find small, helpless Chao trapped in cages. Rescuing these Chao is an optional but rewarding activity. There are three Chao per act, making a total of six Chao per zone. To rescue a Chao, simply run into its cage to break it open. Once freed, the Chao will follow you until you complete the act. If you take damage and lose your rings, the Chao will also scatter, and you'll need to re-collect them. Successfully rescuing all three Chao in an act will often reward you with an extra life or a significant score bonus at the end of the stage.
Some Chao are hidden in plain sight, while others require you to take specific paths, break hidden walls, or use a character's unique ability to reach them. Exploring every corner of a stage is key to finding all the Chao. While not directly tied to the main story, rescuing Chao contributes to your overall completion percentage and can be a fun challenge for completionists. It also encourages thorough exploration of each level, revealing hidden areas you might otherwise miss.
While Sonic Advance 2 tasks players with physically breaking cages to free Chao, Sonic Forces integrates a similar rescue mechanic by rewarding players with cosmetic items.
While Sonic Advance 2 tasking players with finding trapped Chao feels like a simple precursor, Sonic Frontiers modernizes this collectible rescue loop through the discovery of Koco.