In Japanese folklore, the demon that appears as a giant spider and transforms into a beautiful woman is the Jorōgumo.
Jorōgumo is a yōkai, or supernatural creature, whose name is commonly written with characters associated with a courtesan and a spider. Its traditional stories portray it as a deceptive predator that uses beauty, music, or apparent vulnerability to lure men before revealing its arachnid form. Some tales describe it playing a biwa while ensnaring victims in webs.
The creature is often connected with large golden orb-weaver spiders, especially Nephila species. That association can cause confusion with the modern “Joro spider,” the common English name for Trichonephila clavata, an actual spider species named from the same Japanese word. Jorōgumo is also sometimes confused with the tsuchigumo, another spider-related yōkai, but the beautiful-woman transformation is the defining clue here.
Toriyama Sekien included the creature in his 1776 illustrated yōkai encyclopedia Gazu Hyakki Yagyō, helping fix its image in Japan’s visual folklore tradition.