The Kotofurunushi is a tsukumogami (an artifact that has transformed into a yokai) born from an old koto, depicted in the Edo-period yokai bestiary *Hyakki Tsurezure Bukuro* by the artist Toriyama Sekien. Its visual design is highly striking: sorrowful eyes and a mouth emerge on the surface of an old, broken koto that has been abandoned for years, with countless snapped strings hanging down like the tangled hair of a deranged female demon. This is not merely an anthropomorphized object, but a visualization of the intense grudge of an instrument—a tool whose sole purpose is to produce sound—being forced into silence and left to rot.

The deepest charm of this yokai lies in the cruel paradigm shift of Japanese music history hidden within Sekien's commentary accompanying the illustration. Sekien wrote: "Since the blind man Yatsuhashi reformed the melodies, the Tsukushi Koto exists in name only, and those who know its sound are exceedingly rare..." This refers to Yatsuhashi Kengyo, a genius blind musician of the early Edo period. Yatsuhashi Kengyo learned the traditional playing methods of the ancient "Tsukushi Koto," which had previously been played elegantly among aristocrats and monks primarily in northern Kyushu, and dramatically reformed it into a modern style (Sokyoku), gaining immense popularity.

However, as the price for Yatsuhashi's new style sweeping the world, the good old "Tsukushi Koto" became completely obsolete, forgotten by history with no one left to play it. In other words, the Kotofurunushi is not just a monster of an old instrument; it is the incarnation of the sorrowful resentment of "loser's art" (the music of an old school)—eliminated by the advent of a genius (Yatsuhashi Kengyo) and left without an audience. It is an extremely cultural and musicological yokai.