Infernal

The, also known as the , are victims of Spontaneous Human Combustion. Originally humans, the phenomenon causes their bodies to spontaneously ignite, and transform them into a fiery charcoal-like beings that only know destruction. The process of transforming into an Infernal appears to be quite painful and is the most feared cause of death. Infernals are considered to be a dangerous threat to human life and the world, in which the Special Fire Force have been tasked with extinguishing their bodies and purifying their souls.

Overview
Infernals are known to vary as individuals in terms of physical appearance, though they all form around a black figure, enveloped in flames. Some of them are more adept in combat than others and some keep their memories from the time they were humans. Infernals have no reason and rampage until their lives flicker out. They can launch fireballs and control the flames of their own bodies, but they also gain a noticeable increase in strength and agility after their transformation. Infernals have also shown the ability to absorb and redirect the flames around them. The only known way to kill an Infernal is to impale their core, located in their chest, which is a painless method of returning them to the raging flames. Humans also tend to pray for the souls of the defeated Infernals, as a way of purification.

Normal Infernal
This type of Infernal has dark, charcoal skin and is perpetually on fire, although their appearance differs. While typically mindless, an Infernal's behaviour can be influenced by any strong desires or personal connections they had as a human. Meaning that they may remain in a certain area. While powerful and dangerous, they can be restrained by a physically strong human for a short time.

Sentient Infernal
It is known that if a person transforms into an Infernal while having a strong attachment to life or great willpower, they will keep their self-awareness, however the level of consciousness differs between individuals. These Infernals have control over their flames and can discharge them at will, while also being fully capable of speech. It is unclear if they suffer any pain after the initial transformation is over.

Artificial Infernal
Artificial Infernals are humans that were turned into Infernals via unnatural means. Unlike regular Infernals, the heads of the Infernal are the only thing to ignite. After conducting research on Artificial Infernals and natural ones, Hibana discovered that the difference between them was that the artificial Infernals' core (upper body) had been eaten through by the Bug and left some of its biological residue and DNA inside the body. It is believe that the Infernals of immense size with multiple cores are also artificial.

Demon Infernals
, much like normal Infernals, have dark, charcoal skin, but they are defined by the devil-like horns sprouting from their heads. Only a select few can become Demon Infernals under unusual circumstances and seem to trigger a response from the Adolla Link. These Demons are much stronger than normal Infernals, with skin that cannot be the Iai Hand-Sword Style or a plasma blade. As a result, it requires a tremendous amount of power to destroy a Demon Infernal. Compared to normal infernals, they have a much stronger heat signature.

Victims

 * A large outbreak of Spontaneous Human Combustion occurs in Asakusa during Year 194. A Demon Infernal also appeared during this time and was ultimately defeated by Konro.
 * Mikako's mother fell victim to the phenomena in Year 196.
 * A man boarding a train completely transformed into an Infernal and set fire to the train carriage. He was later killed by Akitaru Ōbi.
 * Saeko fully transformed into an Infernal, resulting in the woman damaging her husband's workplace and killing an employee. She was killed by Shinra Kusakabe.
 * Mikako's father transformed into an Infernal while remaining partially conscious through the ordeal. He was soon killed by Arthur Boyle without any resistance.
 * Setsuo Miyamoto fully transformed into an Infernal, murdering multiple innocent people before being captured and experiment on by the Special Fire Force Company 5. He was killed by Arthur Boyle.
 * Masao transformed into an Infernal and was killed by Akitaru Ōbi, with the help of Shinra, some time after the fight between the 5th and 8th Special Fire Brigades.
 * Several Infernals were spotted in the streets under the jurisdiction of the 1st Special Fire Brigade, one of whom was frozen by Karim Fulham.
 * Inside an abandoned building, a woman was artificially turned into an Infernal by Rekka Hoshimiya, who immediately disposed of her afterwards.
 * Hikage's impersonator deliberately exposed himself to a Bug and was turned into an Infernal. He was was swiftly killed by Takehisa Hinawa.
 * Haran chose to turn into an artificial Infernal after being injured in combat, by consuming a Bug.

Trivia

 * The chant that the Special Fire Force preaches before killing an Infernal ("Ashes to ashes, dust to dust") is a phrase taken from the funeral service in the Book of Common Prayer.
 * Infernals, created by artificial means, do not appear to burn through their clothing during their transformation. It is unknown whether this is unique to artificial Infernals only, however, as Mikako's father was also seen wearing clothing in his Infernal-state. This raises questions surrounding his transformation.