The deity of Itakiso Jinja Shrine is Itakeru-no-mikoto, also known as Ooyabiko-no-kami, the god of afforestation.
It is said that God Susanoo-no-mikoto (Itakeru-no-mikoto's father) took tree seeds to Korea but found out that the land there unsuitable for sowing the seeds.
So he brought them back and sowed them in Japan.
In the ancient records of Nihonshoki, there is a legend about the establishment of forests.