Boil Release (沸遁, Futton, Viz: Vapour Style) is a nature transformationkekkei genkai, a combination of fire and water. Whereas most kekkei genkai are largely identical between users, Boil Release has different forms depending on who's using it.
Corrosive vapour is created by Mei Terumī of Kirigakure. Its exact acidity is controlled by Mei and, because it is gaseous, it can rapidly fill confined areas. It is dangerous to enemies and allies alike, dissolving most substances after even brief exposure. In Sasuke Shinden, this form of Boil Release is also used by Futsu.
Steam generated by heating chakra to its boiling point is used by Kokuō and its jinchūriki. The steam emanates from the user's body, either to melt their surroundings or propel them in a direction.