In Japanese folklore, turtle monkey demons can steal your soul… by pulling it out of your anus. Fortunately, they have easily detachable arms and like cucumbers.
The kappa is my favourite Japanese demon, and once you read about it I hope it will be your favourite as well.
Kappa live in rivers and streams and are the shape and size of a small human (or medium-sized monkey). The exact description changes depending on the region and time; it was variously described as resembling an otter, a bipedal fish, a monkey, or a turtle. The most common form, from the Edo period, is green and human-shaped with a shallow concave forehead and a shell back. The forehead depression will be important later on.
But first, that soul thing. Apparently, all humans have a little solid ball of matter in their anus that kappa like to steal. This ball, called the shirikodama, is the physical manifestation of your soul or spirit or essence. Kappa pull people into the water in order to drown them and steal their anus soul ball. One hypothesis about where this bizarre idea comes from is that drowning victims’ sphincters relax, and that makes it look like something had been yanked out? I guess?
Now that you know the stakes, how can you keep yourself safe? Kappa love cucumbers. That makes sense to me. Cucumbers are pretty watery. You could offer the kappa a cucumber to stay their wrath, or write your name on a cucumber and set it afloat to placate them. The sushi roll that contains only rice and cucumber is known as a kappamaki in their honour.
There are more active methods of prevention. As I already mentioned, the kappa have a bowl-like depression in their foreheads. That bowl contains a liquid which is the source of the kappa’s power. If you can trick the kappa into bowing low enough the water will drain out and the kappa will be neutralised. You could do that, or you could just pull its arms off. (The kappa have easily detachable arms. Did I not mention that?) If you refill the kappa’s bowl or give back its arms, it would grant you a boon in thanks.