The mission will start with a tree jumping tutorial. Hold down the free run button, climb onto the leaning tree and afterwards jump to where the branches form a V.
In order to climb higher, you have to press the jump button.
Optional objective: Do not touch the ground or water.
After a short cutscene you will have to reach the stream by jumping between branches. The path is rather simple, but to complete the optional objective you can't touch the ground or water even once. As you run, hold down only the free run button and control your character with the left analog stick.
As you reach the rock at the shore, your friend will start drowning.
Save him and afterwards jump to the tree forming a V growing on the other side of the water.
There you will receive a task of obtaining a feather lying at the top of the rock.
Start off by reaching the rock wall by jumping between branches and the fallen trunk.
Hold onto the ledge and slowly move to the right end of the rock to climb up. don't do it beforehand, as you might fail the optional objective (you'll touch the ground).
At the top, approach the marked nest and press the interaction button.
Optional objective: Find more feathers - 3.
Optional objective: Completed all the constraints in one playthrough.
After falling down you can return to your friend and end the mission, though for full synchronization you still need to collect three feathers.
Two of them will be immediately marked on your map. To get the first one, climb up the bark onto the tree growing in the marked spot.
The item you seek is lying on one of its branches.
From there you can also jump to the second feather.
To get the last one, run towards the green point symbolizing your friend. The feather is hidden south of him and will be marked on the location map as you get nearby it.
After collecting all the items, return to the young Indian to end the mission.