quest name: burden_by_the_shore
Item to obtain: note_from_docter_bride_part2
First of all, you must accept this quest from the quest menu, among the unaccepted quests.
On the Middle_Valley map, turn to heading 270 and cross over using Press_shift_enter_to_enter_the_mountain.
Then follow the camera and climb upward. The camera will guide you at the points where you need to jump.
There are two paths from here.
The first is to follow the camera to the top, then head west and go down to Lake Barrus, and look for the item in the water.
The second is to go through the cave under the mountain and reach Lake Barrus to find the item.