Numawatari

Numawatari (沼渡, "Migratory Ponds") is a yokai who insinuates itself in ponds devouring everything that is in, or near, humans, animals, fish and birds. Even the water is eaten and at the end Numawatari himself becomes the pond. He migrates from one pond to another. The particular ability of this demon, that is to be water, it makes it invulnerable to attacks powerful. Appears only in the manga.

Synopsis
The first people to approach the turbid pond of Numawatari are Rin, Jaken and Sesshomaru. The little Rin is thirsty and wants to drink from the pond, but Sesshomaru 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 hanyo 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 Bakuryuha 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 yoki 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, Sesshomaru, outraged by the way in which Tessaiga is used by his brother, kills Numawatari with Meido Zangetsuha, still incomplete, sending him and all the water in the underworld, after having defined the water demon one yokai low level.