The area leading up to Pyou's cabin is pretty straight forward and there are no chests. You'll meet Pyou and go through a scene where you'll also meet Bisou, the third playable character. There's a mini boss battle, then you'll get a third crystal. Pyou will have taught you how to use crystals. Open the pause menu and click the crystals button at the bottom left to buy skills with crystals. Once you've bought them, some of them need equipping in the Abilities menu.
Head back across the bridge and to the North East.
Enemies in this area are ants, bazooka ants, tough ants, birds and wolves. The mini boss battle is against two machete ants.