The Tree Who Stands Alone is a quest in Mingyun Village, a mining site that's been long abandoned. You'll find the ghost of Yuan Hong in the ruins, near the notice board. After a short conversation, you'll need to go to the south of the village to find the 'Lost Notes,' which will spawn the rest of his will. You'll find one in a cave near a pond. There's a Hilichurl inside and some explosive barrels. Blasting the barrels will open a new area to explore. It contains the will, some ascension materials, and a Luxurious Chest. Another one may be found in a cave to the east of the village, somewhat northwest of the nearby domain. There is a nearby chest guarded by Hilichurls, or none if you've defeated them and picked up the treasure already. Go inside the cave and pick up the will. A cave to the north holds a piece of the will. There are some Geo Slimes and a Hilichurl along the path. You can skip them by swimming or sprinting across the water (with Mona or Ayaka). The last area is a cave with two entrances under heavy guard to the west. Defeat them and pick up the will so you can find the treasure. Three Treasure Hoarders guard the treasure's location, a tree nearest to the western cave. This quest unlocks the achievement "Trees Should Blend Their Roots and Shade, For That Is Where The Home Is Made." It adds an additional 5 Primogems to the quest reward of 50. Upon finishing it, you can also get some Adventurer EXP and a Liyue Shrine of Depths Key.