Koto-furunushi

Koto-furunushi belong to the tsukumogami class of Japanese folklore — crafted objects that acquire spirit after long use (commonly said to be around their 100th year). The archetype is an old koto that, when treated with consistent respect, becomes animated as a benign yōkai. A regional legend recorded for Saga Prefecture (Kanzaki) tells of an imperial gift-koto that transformed into a majestic camphor tree whose treetop emitted faint zither music for passersby; that account also holds that the 'ghost of the camphor tree' can dive into very old kotos to animate them. Sources for these elements include summaries and folklore compendia of tsukumogami and the specific Kanzaki/Saga tale as cited in modern references.

The koto-furunushi appears as a traditional koto (Japanese zither) that develops a demonic face on its front surface. Its strings are described as beginning to meander in all directions, likened to an uncombed mane. The transformation is an alteration of the instrument itself rather than a separate humanoid form; descriptions emphasize the koto's retained instrument shape even as facial features and disordered strings give it an animate, eerie aspect.

When it reaches its century milestone and has been consistently cared for, the koto-furunushi will animate and play by itself, producing extraordinarily enchanting music — especially when no one watches. It tends to play the pieces that were performed on it most often and with special devotion, effectively preserving the musical memory of its players. If neglected by an owner, the instrument may become sorrowful and is said to seek company from other tsukumogami, playing for them and eventually forgetting the neglectful owner. Sources explicitly describe the entity as harmless to humans. Accounts note that it is not handed down whether the koto-furunushi can move on its own beyond animating its music.