Suiko are found in both China and Japan and are often confused with kappa, which they closely resemble. However, suiko are far more dangerous, violent, and hot-tempered than their kappa cousins. Suiko have the body of a small child and are covered in extremely tough scales like a pangolin’s. They have sharp, hook-like growths on their kneecaps which resemble a tiger’s claws. They live near riverbanks and in large bodies of water.

Suiko rank above kappa in the hierarchy of water goblins, and as such are sometimes placed in charge of them, with one suiko placed in charge of 48 kappa. They are sometimes called the oyabun, or yakuza bosses, of kappa. In turn, suiko report to the Ryū-ō, the dragon king, who lives in his palace, Ryū-gū, at the bottom of the sea. The reason suiko kill humans is to look tougher among the other suiko and increase their standing with the dragon king. Likewise, when kappa attack humans, it is to make them look tougher and increase their standing with their suiko boss.

Suiko who live in inhabited areas like to sneak out of the water at night to play pranks oh humans, knocking on doors and running away, or possessing people and making them do strange things. Like kappa and other water spirits, suiko enjoy using their superior strength to pull humans into water and drown them, although unlike kappa they have no concern for the shirikodama. Instead, suiko drain their victims of blood like vampires, then eat their souls (reikon) and return the dead, drained body to the surface.

It is possible to keep suiko at bay by leaning a sickle against the side of a house and sprinkling flax seeds or black-eyed peas on the ground outside. Suiko are afraid of these and will keep away.

There is one known method to kill a suiko. It involves the corpse of a person who has had their blood drained by a suiko. First, a small hut made of grass and straw is built in a field. Then the body, instead of being buried, it is laid on a wooden plank and placed in the hut. The suiko who sucked that person’s blood will be drawn to the hut, where it will start running around and around in circles. Suiko have to ability to become invisible, so it is likely that it will only be heard rather than seen; or else only its footprints will be visible. As the dead body gradually decays, so will the suiko. By the time the body has rotted completely, the suiko will have died, its magic will have ceased, and the decayed corpse of the suiko will be visible on the ground near the body.