Water Release: Black Rain Technique

This technique creates a flammable black mist that forms a small cloud. The user can then move the cloud above their target and disperse it, covering the target in flammable oil. This technique was first used to burn down Idate Morino's boat, after it was lit with fire.

Trivia

 * Although it is just an anime-filler technique, it is similar to Amaterasu and Black Lightning in that it is the only other black-coloured elemental technique.