Hyotan-kozo (literally, a calabash or bottle gourd boy) is one of Japanese yokai (ghosts, spirits and monsters) that was transmuted from a calabash or bottle gourd. It is considered to be a kind of tsukumogami (a type of Japanese spirits that originate in items or artifacts that have reached their 100th birthday and become alive).
Sekien TORIYAMA's "Gazu Hyakki Tsurezure Bukuro" (The Illustrated Bag of One Hundred Random Demons; the term 'hyakki' in its title is a pun on the usual hyakki, replacing the character for demon which is written as "鬼" in Japanese with a character for vessel written as "器," and sure enough, most of the yokais shown in this book are tsukumogami) portrays the Hyotankozo in a human-like figure whose head is a bottle gourd, along with a Nyubachibo (literally, a mortar [a bowl-shaped vessel] bonze). From ancient times, Japanese people have believed that spirits and souls may easily stay in a hollow object, such as a bottle gourd. There are magical folk beliefs, such as hanging gourd may prevent diseases and growing gourds in the yard may cause a disaster. The gourd which was possessed by an evil spirit became a yokai, which may also be called the Hyotankozo.
Some say that it appears suddenly out of a thicket and frightens people.