画図百鬼夜行
In the collection of yōkai depictions, the "Gazu Hyakki Yagyō" by Toriyama Sekien, under the title 木魅 ("kodama"), an aged man and woman are depicted standing alongside the trees and here it is stated that when a tree has passed a hundred years of age, a divine spirit would come dwell inside it and show its appearance. According to the 13th century Ryōbu Shinto manual "Reikiki", kodama can be found in groups in the inner reaches of mountains. They occasionally speak and can especially be heard when a person dies.