thumb|A kappa in [[ukiyo-e art.]]
In Japanese folklore, the is a familiar type of water monster, considered one of three major yōkai.
Providing labor
In other legends, the kappa has helped out with public works, e.g., with the swampland reclamation project around Sōgen-ji temple, cf. . Already in the Wakan sansai zue (1712) it is stated that kawatarō "steals squashes, eggplants, and cereals from the fields<!--瓜・茄・圃穀-->", while the Honzō kōmoku shakugi records its favorite foods as cucumber and (variety of persimmon). A similar observation has been made by Minakata Kumagusu.
Legend or folktale exhibiting this motif is ubiquitous and found from the Tōhoku region (Iwashiro Province, Rikuchū Province), Kantō region (Hitachi Province, Musashi Province, Sagami Province), Chūbu region (Echigo Province, Suruga Province, Mikawa Province, Kai Province, Shinano Province, Hida Province, Mino Province, Noto Province）, in Yamashiro Province (Kyoto), Harima Province (Hyōgo Prefecture), Chūbu region (Izumo, Nagato Province), Shikoku (Awa Province, Tosa Province), Hizen Province (Saga and Nagasaki prefectures), etc.
As in the Izumo version, many versions call for the kappa to be dragged by the horse to the stable where it is most vulnerable, and it is there it is forced to submit a not to misbehave.
Already the Wakan sansai zue (1712) has recorded the folklore that the kawatarō makes use of his stretchable arm to draw in cattle and horses, sucking all blood from the rumps.
Weaknesses
The kappa reputedly abhors iron and deer antler.
Wintering in the mountains
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In certain parts of the Japan, the appearance of the kappa in rivers is considered seasonal, as they are partly mountain-dwelling. But its original source was the shuihu ("water tiger") described in from the Chinese pharmacopeia Bencao gangmu, which according to the latest English translation, describes it as having tiger-like fur on the head and knees.]]
The image of the kappa before the 18th century appears to have favored the ape-type (furry, mammalian type), and non-herp types. For instance in the Kagakushū<!--下学集--> ("Collection of Low/Mundane Studies", prefaced 1444, with later copies), it is claimed that the otter grown old becomes a (kappa), and in the Nippo Jisho (Japanese-Portuguese dictionary by the Jesuits, 1603) the entry for defines it as an ape-like creature.
Another prime example of the turtle-froglike kappa<!--given by Ozawa 2011-=> is that represented by Toriyama Sekien's Gazu Hyakki Yagyō (An'ei7/1778). Sekien here depicted a scale-covered creature with (stripe) marks, and from copies made, these were all of the hairy ape-type (as explained below).
When afterwards ed. appeared, it offered a collection of 12 kappa anecdotes, of which 6 were a rehash from the Hita Domain report, so that the 6 accompanying illustrations have been judged to be facsimile copies of the original color-painted drawings. These 6 are all kappa of the ape-type (covered with fur), with a dish on its head, somewhat like a tonsure, but with untidy strands of hair hanging loose on the side. One kappa figure is shown wearing a sumo wrestler's loincloth (mawashi). On the page opposite to it, there is a detailed drawing of a webbed foot, so that might count as technically as the 7th drawing copied. The other half of the kappa illustrated in Suiko kōryaku are 6 illustrations of the "softshell turtle-type".
Another turning point in pictorial representation occurred when naturalist Kurimoto Tanshū (d. 1834) published his depictions of the kappa in his work , which showed the creature with a tapered mouth, probably based on a life drawing from a real softshell turtle. Tanshū also authored the (date unknown, a Tenpō 13/1843 copy is extant).]]
A kappa by Katsushika Hokusai in Hokusai Manga, Volume 3
The tendency to identify the kappa as the principal enshrined being at suijin festivals appears more prevalent in Western Japan, while at the of Nankoku, Kōchi enshrines a kappa by the name of enkō.
Kyūshū region
In Kyūshū there is a legend concerning , the name of a kappa boss. Kusenbō (whose name means "Nine-thousand fellow") had 9000 underling kappa, and was based in the Kuma and Chikugo River holding dominion over all of Saikaidō (Kyūshū). Legend has it that the warlord Katō Kiyomasa angered by the Kusenbō gang's misdeeds gathered all the apes he could from Kyūshū to help subdue them.