Where to Search for the Shades in Village: NieR Replicant Quest
Speak with the guard near the southern exit of the Village Market area. You can pick this quest only after obtaining Aeries key fragment. Guard needs your help in locating shades that have infiltrated the Village and kill them.
Then a girl near the guard tells that she saw shade/monster at the village river. Heads to the west side of the river but you will not find any shade there.
Again, go back and talk to the girl and this time she will send you to the library. But there too you will not find any shades.
Now, talk to the other three villagers in the market area to locate the shades and lastly again with the same girl.
This time she will tell that she didn’t see shades on the hill. This is the location of shades actually. (Use stairs near the market entrance and go west).
You can reach the hills by the stairs near the town entrance and continuing west. You’ll find the shade up on the hill here, deal with it then return to the guard to complete this quest.