Numawatari

was a yōkai who insinuated itself in ponds devouring everything that was in, or near, humans, animals, fish and birds. Even the water was eaten and at the end Numawatari himself becomes the pond. He migrated from one pond to another. The particular ability of this demon, that is to be water, it made it invulnerable to attacks.

History
The first people to approach the turbid pond of Numawatari are Rin, Jaken and Sesshōmaru. The little Rin is thirsty and wants to drink from the pond, but Sesshōmaru stops her, then seeing a bird that is devoured.

The group of Inuyasha goes instead to examine the pond because informed by the villagers of the village. The hanyō with Kaze no Kizu hits the pond to flush out the demon. Numawatari controlling the water creates vortices and shape of his face. Inuyasha tries to attack him with the Bakuryūha and the Kongosoha, but both techniques are ineffective because the demon is made of water.

Only with Dragon-Scaled Tessaiga can of succeeding effect, absorbing the yōki of Numawatari, but the demonic energy is too large. Miroku tries to absorb all the water with the Kazaana, but even he is forced to stop because it is likely to remain tainted by the aura malignant.

At this point, Sesshōmaru, outraged by the way in which Tessaiga was used by his brother, kills Numawatari with Meidō Zangetsuha, still incomplete, sending him and all the water in the underworld, after having defined the water demon one yokai low level.