Tradition: Japanese Mythology
Alternative Names: 旧鼠, Old Rat, Aged Rat
Category: Rat
The Myth
Kyūso refers to an old rat that has acquired supernatural qualities through age. It appears in Japanese works such as Ehon Hyaku Monogatari and Okina gusa, where it is associated with extraordinary strength, unusual behaviour, and strange relationships with cats and humans.
In Ehon Hyaku Monogatari, one account describes a rat from Shigi in Yamato with red, black, and white fur that habitually caught and ate cats. Another tale, set in Dewa during the late fifteenth century, tells of an old rat that had lived undisturbed in a stable for generations. After the household cat died from poison, the rat reportedly nursed and raised her five kittens before eventually disappearing. This remarkable story was passed down to Matsuo Bashō through Kawai Sora. The same book also references a tale from the Chinese collection Taiping Guangji involving an old rat that entered into a relationship with a human woman.
A different account in Okina gusa, set in Nagoya around the beginning of the Hōreki era (1751–1764), describes a gigantic old rat that repeatedly stole oil from a household lamp. When confronted by cats, it killed one by biting its neck. Eventually, however, another cat defeated the rat by remaining still until the creature attacked, then killing it with a bite. These stories portray the Kyūso as a formidable creature whose extraordinary age grants it unusual abilities, while also exploring the shifting relationship between cats and rats.
Sources
“Kyuso.” 新版TYZ 妖怪図鑑 (New TYZ Yokai Encyclopedia). https://tyz-yokai.blog.jp/archives/1076714120.html