Go to forest one and talk to the rappy you see at the beginning (yellow circle). The screen will turn black and the rappy will disappear. Folow the path to the room with another rappy you can talk to (yellow circle). Once again the screen will turn black and the rappy will disappear. Continue to the last rappy (yellow circle) and talk to it 3 times. It will confess to being Dr. Guls in disguise. Take the pipe to Pioneer 2 and talk to Dr. Guls's assistant to finish your quest.

Check here for enemy counts.
Check here for quest experience counts.

If you are trying to find the Lost Chao for Sonic Adventure 2, check here.