Kappas, although they’re thought to be only the size of a child, evidently enjoy exhibiting their strength in the form of sumo wrestling, and often challenge people to matches. if they win, it’s a safe bet the losers are dragged into the water, but if the kappa is the one who loses, they will keep on challenging until they win.
How strong can a kappa be you ask? One of the most well-used analogies is that they’re strong enough to drag horse or a cow into water.
Kappas are capable of becoming invisible, or even transfiguring into animals or people. It’s believed they can also ‘possess’ humans or animals. If a kappa enters a child’s body, the child will spend all day staring at a nearby river or lake, until they wander into the water and drown.
Regarding the origin of the kappa, there are several explanations. One of them is of overseas migration, where kappas were believed to have lived in the Yellow River in China, and in an effort to find a better habitat they moved eastwards until they arrived in Kyushu (九州). The kappas started to expand in numbers, reaching a population of more than nine thousand, and their leader was known as Kuzenbou (九千坊). He ransacked the villages, creating chaos everywhere until one of the feudal lords, to destroy Kuzenbou, created an army from the kappa‘s nemesis – monkeys. The kappas left and settled down in Fukuoka with the then-leader’s permission, and eventually became messengers to water kami.
Source: 日本神妖博物誌 作者： 多田克己 譯者：歐凱寧