Kotofurunushi is one of Japanese specters that is introduced in "Hyakki Tsurezure Bukuro" (One hundred bags in idleness) which is a collection of specters illustrations by Sekien TORIYAMA, and it is Tsukumo-gami (gods to a variety of things) of koto (a long Japanese zither with thirteen strings).
It is thought that Tsukushi goto (koto music from the Tsukushi area of Kyushu), one of sokyoku (koto music), has become obsolete, and when even its tone has been dismissed from people's minds, the koto which played the music of tsukushi goto transformed itself to a specter. Also, in "Hyakki yagyo emaki"(picture scroll of Hyakki yagyo) from Muromachi Period, since a speter of koto is depicted, it is said that Sekien has depicted kotofurunushi on the basis of "Hyakki yagyo emaki".
Furthermore, there is also such a theory shown below that Kotofurunushi is a folklore from the era of Emperor Keiko. From the orders of Emperor Keiko, his vassals set up a place for a banquet on a hill at the southern part of Kanzaki County, Saga Prefecture. The Emperor was in joy with the banquet, and placed the koto on top of the hill in commemoration. Then, the koto transformed itself into a camphor tree lush with green leaves. Since then, on passing by near this tree at night, the sound of koto has come to be heard out of nowhere, and before being realized, the tree had begun to be called as the tree of Kotofurunushi.