Futton: Boil Release in the Naruto Universe

How It Works

The Boil Release (沸遁) is a combined chakra nature, created by simultaneously using Fire Release and Water Release. It is classified both as a kekkei genkai and as a ninjutsu. It first appears in chapter 466 of the manga, then in episode 204 of Naruto Shippuden; the novel Sasuke Shinden: Book of Sunrise gives it a user found nowhere else, and the game Naruto Shippuden 3D: The New Era is its first video game appearance. Four media therefore document it: manga, anime, novel and game.

The name raises a translation question. Literally, 沸遁 means "Boil Release"; the Viz edition and the English dub nevertheless went with "Vapour Style", and it is the dub alone that renames the Komu no Jutsu "Solid Fog Jutsu". French followed the steam reading, whereas the kanji 沸 refers to boiling water. The gap is not trivial, because the two words cover two very different manifestations of the same kekkei genkai.

Only one Boil Release technique is credited with a hand sign: the Komu no Jutsu, formed on the Horse sign before the mist is expelled through the mouth. The techniques tied to Kokuo mention none. Boil Release is moreover attached to no clan: unlike the Ice Release (Hyoton) of the Yuki clan or the Wood Release (Mokuton) of Hashirama Senju, nothing gives it a named bloodline.

A Kekkei Genkai With Two Faces

Boil Release calls for a caveat from the outset: where most kekkei genkai are largely identical from one wielder to the next, this one takes different forms depending on who uses it. Two are documented, and all they have in common is the pair of natures involved, water and fire. Nothing links their wielders by blood, or assumes a single origin for them.

The first is a corrosive steam, created by Mei Terumi of Kirigakure. Its exact acidity is set by the user, and because it is a gas, it fills confined spaces very quickly. One point counts: it is dangerous to enemies and allies alike, and dissolves most substances after even brief exposure. In the novel Sasuke Shinden: Book of Sunrise, this same form is used by a second shinobi, Futsu.

The second is a steam obtained by bringing chakra to its boiling point, and it belongs to Kokuo, the Five-Tails (Gobi), as well as to his jinchuriki. It is not projected at a target: it emanates from the user's body, either to melt what surrounds him or to propel him in a given direction. A mist spat out on one side, a cloud given off on the other: the same kekkei genkai produces two things with nothing in common in form or in use.

Mei Terumi and the Corrosive Mist

The Boil Release: Komu no Jutsu (沸遁・巧霧の術) is the technique through which Boil Release enters the story. The user creates a cloud of mist that she releases through her mouth. This mist is highly acidic: it melts bodies, but also chakra defenses and barriers, which it simply cancels out. The fourth databook, page 292, frames the fact as a notable exception, the Susanoo being held to be an "absolute defense".

Two properties follow from this, and the Fifth Mizukage exploits both of them. The exact acidity of the cloud can be adjusted, and the user appears immune to her own gas, since Mei uses it in an enclosed space without putting herself in danger. The effect, however, is indiscriminate: that is the inherent drawback of the technique, which restricts its use to areas empty of allies. Its page knows only two wielders, Mei and Futsu.

One confusion is worth clearing up. Mei can hide her own movements and those of her allies behind a screen, but that does not come from Boil Release: it is the Kirigakure no Jutsu, the technique for hiding in the mist, used in chapter 563. The Komu no Jutsu, for its part, hides nothing. It is classed as offensive and supplementary, of short to mid range, and works as a saturation of the space, not as a screen.

The Sealed Hall at the Five Kage Summit

On the page, the corrosive form unfolds at the Five Kage Summit. Sasuke Uchiha, who has come to kill Danzo Shimura, is first stopped by Mei's Lava Release (Yoton), then pushed back by Chojuro and his Hiramekarei blade into an adjoining hall. Mei shuts herself in there with him and fills it with mist. The setup says everything about the technique: for it to show its full measure, it needs an enclosed volume and no ally inside.

The gas acts fast. Weakened, Sasuke watches the ribs of the chest of his Susanoo melt before his eyes, in chapter 466, page 7. What the scene establishes is not a balance of power between two characters, but a property of the mist: it passes through a chakra defense that the databook ranks among absolute protections. Mei does not finish off her opponent, however, because Zetsu's spore technique catches her off guard and transfers her chakra to Sasuke.

What follows documents the limit rather than the power. Sasuke breaks a wall, the mist threatens to leak toward the other Kage, and Mei changes its pH so as to hurt no one, on page 12 of the same chapter. This gesture proves her sense of honor; on the technical side, it above all confirms that the acidity of the cloud remains controllable after release, and that she herself apparently suffers nothing from it.

Futsu, Boil Release Outside the Manga

Outside the manga, only one story gives Boil Release an additional wielder. Futsu is a shinobi whom his master, En Oyashiro, presents as the strongest of those he owns. He fights at the Coliseum, an underground arena set on an island missing from every map, where the loser becomes the property of the winner's master and where fighters with a kekkei genkai are worth the most. In the anime, Sasuke lands there by boat, with Orochimaru and Team Taka.

His opponent is Sasuke Uchiha, and the novel explicitly motivates the outcome: having already faced a Boil Release user, Sasuke beats him easily with the Great Fireball Jutsu. He then refuses to claim ownership of him, asks only to meet Oyashiro, then demands a rematch once Futsu has been treated for his light injuries. It is on this second victory that he gives him back his freedom.

The anime gives another version. The novel Sasuke Shinden: Book of Sunrise becomes a five-episode arc there, 484 to 488, where Futsu appears in 485: the duel is interrupted by the sudden arrival of exploding humans, and the freeing of the fighters falls to a Kumogakure raid led by Sasuke, whereas the novel entrusts it to Kirigakure and to Chino. The freed fighters reach Konoha with Yamato's help in the novel, Kumogakure in the anime.

Kokuo, the Steam That Comes From the Tailed Beast

Kokuo, the Five-Tails, produces Boil Release by combining water chakra and fire chakra, not to spit out a mist, but to bring his own chakra to its boiling point (chapter 684, page 5). This ability founds what is called "steam ninjutsu", which gives the beast as well as its host overwhelming physical strength. In use, the jinchuriki gives off abundant amounts of steam.

The corresponding technique page is the Boil Release: Kairiki Muso (沸遁・怪力無双, "Unrivaled Strength"), fourth databook page 326, classed at once as ninjutsu, taijutsu and fighting style. It begins in chapter 565 of the manga and in episode 325 of Shippuden. Its rule is arithmetic: the strength obtained is proportional to the volume of steam released, and the discharge increases not only the user's power, but also his speed.

A third effect follows from the rise in temperature: all water and all ice in direct contact with the body evaporate (chapter 684, pages 4-5). This is not narrative decoration, for it is precisely the property Naruto Uzumaki will draw on in Kaguya's ice dimension. The mechanism is the same for the beast and for the host: the combined nature belongs to the tailed beast, and the human has access to it only through its chakra.

Han and the Steam Armor

Han, jinchuriki of Kokuo and shinobi of Iwagakure, is the only Boil Release wielder to work through a piece of equipment. His steam armor (蒸気の鎧, Joki no Yoroi) appears in chapter 515 of the manga and in episode 205 of Shippuden. It covers his entire body and houses, on the back, a furnace where the steam borrowed from Kokuo is stored in large quantities before being released. His fighting style appears to rest on taijutsu.

The role of the furnace is to delay the release. By adjusting the amount and the pressure of the accumulated steam, Han considerably amplifies the force behind his blows, as pages 8 and 9 of chapter 564 show. The rule of proportionality holds here as elsewhere: the greater the volume used, the stronger the pressure built up in the armor. What the furnace can hold therefore bounds the strength available.

His reputation goes back to the Third Great Ninja War. The fourth databook reports that Han had become known the world over for his mastery of steam ninjutsu as early as that conflict, and places both his speed and his taijutsu power among the greatest in the world during his lifetime. The armor therefore equips a close-combat fighter, and not a caster of long-range techniques.

Han, Boil Release Against the Allied Shinobi Forces

During the Fourth Great Ninja War, Han's Boil Release is used against the Allied Shinobi Forces. Brought back from the dead by the Edo Tensei (Reanimation Jutsu) of Kabuto Yakushi, he is then turned by Tobi into one of his Six Paths of Pain: Rinnegan in the left eye, Sharingan in the right eye, tailed beast resealed in the body and chakra receiver driven into the flesh.

The fight takes place in chapters 564 and 565, adapted into episodes 324 and 325. Blinded by Fu's scale powder technique, Naruto Uzumaki and Killer Bee are attacked head-on by Han and Yugito Nii. The first exchange is telling: Han's fist is blocked, and it is only then that he releases the steam from his armor, after which he overpowers Naruto through physical strength alone.

The second intervention is more telling still. When Naruto tries to destroy the chakra receiver driven into the chest of Roshi, Han intercepts him with a steam kick that sends him backward. The effect of this kind of blow can be measured: with a large volume of steam, a single kick sent Naruto in Nine-Tails Chakra Mode and Killer Bee, who had only just caught up with him, flying far away. Boil Release hides nothing here: it strikes.

Naruto Uzumaki, Boil Release Without a Bloodline

The manga gives Boil Release a wielder that no bloodline explains. After receiving the chakra of the tailed beasts, Naruto Uzumaki can use Shukaku's Magnet Release (Jiton), Son Goku's Lava Release and Kokuo's Boil Release. The scene is dated: in the ice dimension of Kaguya Otsutsuki, he receives a share of the Five-Tails' power, frees himself from the Rabbit Goddess's trap and drives her far back, in chapter 684 as in episode 470 of Shippuden.

The form drawn on is Kokuo's, chakra brought to a boil, which evaporates the water and the ice in direct contact with the body. The technique itself, a massive cloud of boiling steam that surrounds the user and burns whatever comes near, remains unnamed in the manga as in the anime. It was named Boil Release: Joki Bakuhatsu (沸遁・蒸気爆発, "Steam Explosion") only by the game Naruto x Boruto: Ninja Voltage.

Naruto is also credited, alongside Han, with the Funsuiken (噴推拳, "Eruption Propulsion Fist"), a steam-boosted punch seen in chapter 564 and in episode 324, likewise named by a game, Ultimate Ninja Storm 3. The scope of this case goes beyond anecdote: Boil Release is described both as a characteristic of the Five-Tails and as a kekkei genkai of the Fifth Mizukage. Naruto falls under the first path, without a bloodline.

Strengths and Limits

The limits described are few, but precise. For the corrosive mist, the documented constraint is its indiscriminate nature: that is the inherent drawback of the technique, which can only be used in an area empty of allies. Its gaseous nature cuts both ways, since it fills a confined space very quickly, which makes it above all a weapon for closed rooms.

The countermeasure exists, and it is internal: if the gas leaks out of the confined area, the user can bring the pH of the mist back to a harmless level, as Mei does in chapter 466, page 12. In the other direction, the acidity can be pushed up. No particular chakra cost and no learning difficulty of its own are assigned to Boil Release: those assessments appear nowhere.

On the strength side, the mist cancels chakra defenses and barriers, including those the databook ranks among absolute protections, and the steam form increases the user's power as well as his speed. Its measure remains arithmetic: since the strength obtained is proportional to the volume of steam released, it is bounded by what the user can produce and store, hence the value of Han's back-mounted furnace.

What the Games Named

The real question in this section is not the variety of the techniques, but their status: who named what. Several Boil Release moves do exist on the page without carrying a name, and it is the video games that named them after the fact. The Funsuiken and the Fungokyaku, Han's steam punch and steam kick, are seen in chapters 564 and 565 but named only in Ultimate Ninja Storm 3.

Others exist only in the games. The Komu no Jutsu – Henryu condenses the mist into a single cloud that advances on the opponent, and it is exclusive to Ultimate Ninja Storm Generations. The Boil Release: Kazan no Jutsu (沸遁・華懺の術) makes pockets of corrosive steam rise from the ground, which the user then detonates one by one, and belongs only to Ultimate Ninja Impact; there is a homophony there, since "kazan" written 火山 means volcano.

The trickiest case is the Joki Bakushin (蒸気驀進), a steam charge that mimics the motion of a locomotive, whistle included. It comes from Naruto Online, and its animated appearance in episode 430 is not Han's: it is the Han dreamed by Killer Bee under the Infinite Tsukuyomi. Storm 3 also names a series of moves belonging to Han alone, from the Funkoto to the Funjinshin, with no counterpart on the page.

What a Combined Nature Requires

Nothing describes a learning path for Boil Release, no preparatory exercise, no step-by-step progression. What is described is the condition of access. Combining two basic natures simultaneously to create a third from them, one that does not otherwise exist, presupposes a genetic aptitude, that is to say a kekkei genkai: chapter 316 establishes it, the Sha no Sho (Naruto databook) confirms it on page 217. Three combined natures would fall under a kekkei tota.

An ordinary shinobi is not helpless for all that. He can use two chakra natures in tandem in what the Jin no Sho (Naruto databook), page 328, calls a yugojutsu, a fusion technique. The operation is not the same: fusion juxtaposes two effects where the kekkei genkai manufactures a third. The anime adds, in episode 55 of Shippuden, that the wielders possess an affinity for the natures they must use together, and Shikamaru Shinden credits them with two chakra "attributes" where the others have only one.

Hence an apparent contradiction, which has to be settled. In chapter 466, Mei states that she uses three natures, fire, water and earth, hence her two kekkei genkai, whereas the Jin no Sho, page 186, credits her with four, including Lightning Release (Raiton). One concludes that she was speaking of affinities and not of accessible natures. The same reading holds for Yamato, who says he is limited to two when the same source recognizes three in him.

Boil Release Among the Combined Natures

Only one comparison really holds. Boil Release is one of the three combined natures described both as a characteristic of a tailed beast and as a shinobi kekkei genkai: Magnet Release for Shukaku, Lava Release for Son Goku, Boil Release for Kokuo. The six other combined natures shown in the manga do not have this dual membership. They are also the three combined natures that Naruto gets from the tailed beasts, one per beast.

The second sourced connection concerns Mei Terumi, who carries two of these combined natures, and it comes down to one word: both corrode. Her lava partly melted the ribs of the chest of Madara Uchiha's Susanoo in chapter 563; her mist pierced Sasuke's in chapter 466. Her lava techniques are even written with the kanji 溶, "to dissolve", while those that manipulate molten rock or ash are written 熔, "to melt".

What is not said is worth noting. The performance of Boil Release is not compared with that of any other combined nature, sits in no hierarchy of power and carries no advantage against a given element. The only documented relational framework remains that of the nine tailed beasts and their hosts, where one and the same combined nature can come from a bloodline or from a beast, with Boil Release illustrating both cases on its own.

Summary Table