Setsuo Miyamoto

is a former firefighter, who turned into a sentient Infernal.

Appearance
As a human, Setsuo was a bald middle-aged man with a stubble and a very devious appearance. He was last seen wearing a prison uniform, given that he was a criminal. When he turned into an Infernal, his skin turned dark blue and the area above his cheek disappeared, leaving a vertical lining similar to a thick antenna above his mouth. Though he has no scalp, the area behind the 'antenna' has flames around it. Setsuo had a very muscular physique and wears white trousers with black shoes. The majority of his facial features were composed of his mouth, though he has no lips and his large teeth were always visible. Through the transformation, the handcuffs he was wearing turned into flames alongside him, which he used for combat. During his encounter with the Special Fire Force Company 8, a small part of his face was blown off by a gunshot from Takehisa Hinawa and his right forearm was cut off by Shinra Kusakabe. After Setsuo was taken in by the Special Fire Force Company 5, he gained a large white cloak, the uniform trousers of the Special Fire Force, and the number "5" on his head. He also gained an armament, attached on the missing part of his arm.

Personality
As a human, Setsuo appeared to be a troubled and psychologically disturbed man, and was dubbed insane after becoming a serial killer. Setsuo had no concern for the well-being of others, as he recklessly directed his flames and burned two people, and displays ill intent. As an Infernal, Setsuo retained his psychotic behaviour to an extent and became driven with killing everyone in sight, bringing them painful death in the process. Though he possessed a strong killing-intent, as he was able to keep his consciousness, he thought about his actions tactically, proving he has some intellect, as shown when he chose to give up when faced against the 8th Special Fire Brigade, showing that he valued his life dearly. Setsuo had shown to have a strong opinion on Special Fire Brigades themselves, comparing them to murderers. As Setsuo kept his sentience after his transformation, he considered himself a life form just as important as human beings. He was willing to deceive others in order to achieve his goals.

Abilities
Setsuo transformed into an Infernal while having a strong attachment to his life and as such he maintained his strong consciousness and self-awareness. Using the flames around his wrists and from his head, he was able to fly and launch fireballs. Setsuo could also use the flaming handcuffs as malleable flames to suffocate opponents or use them for offensive attacks. He had a fit physique and had shown to be able to punch through Sputter Comet☆ with ease. After being taken in by the 5th Special Fire Brigade and being experimented on, Setsuo was blessed with an armament on what remained of his right arm, which allowed him to concentrate all of his firepower to create an extremely powerful blast, heading in a singular direction.

Background
During his time as a firefighter, Setsuo became mentally disturbed and managed to kill four innocent people for his personal amusement. In court, he acted like he lost his sanity.

Introduction arc
On the final day of his trial, Setsuo is deemed not guilty for the actions he had done in the past, by reason of insanity. As he leaves the court, Setsuo begins turning into an Infernal. In the midst of his transformation, the man kills two people, who laugh at his misfortune. As he fully transforms, he angrily declares that he'll kill everyone. Setsuo continues his rampage by killing an innocent person and the judge of the courthouse. He then leaves the court as he takes his lawyer hostage. The Infernal encounters Shinra and Arthur, who work together to fight him. During the fight, Setsuo notices a woman, who happens to be present on the scene, and progresses to use his flames on her, but Maki stops his attack.

When the Infernal attempts to surrender, hoping that his life would be spared, Takehisa shoots him. In retaliation, Setsuo uses such an opportunity to distract his opponents and flee the scene. After escaping, he attempts to kill a passerby but is intercepted by Shinra. Setsuo tries to reason with him and launches a car at three bystanders, but Shinra reflects it back. Realising the predicament he's in, Setsuo requests a sister to pray for his soul before his death. When Shinra turns his back, the Infernal attempts to attack him, but loses his right forearm in the process. Afterwards, Hibana arrives to intercept Shinra's finishing blow, saving Setsuo from jeopardy. Hibana orders her brigade to capture Setsuo in hope of studying him in the future.

VS. 5th Special Fire Brigade arc
After the confrontation of the 5th and 8th, Setsuo was brought back to the headquarters of Company 5, and was violently experimented on by Hibana. During the experimentation, Setsuo pleaded for her to stop and exclaimed that something was going to come out of him if she carried on. While being experimented on by an elderly brigade member, Setsuo was given drugs that increased his strength exponentially and was fitted with an armament in place of his missing arm. At the time of the 8th infiltrating the Combine, Setsuo and Conehead confronted Arthur. Setsuo displays his new powers by easily handling Arthur during the fight, shocked by how weak he is. In the lasting stages of the fight, Arthur finally recalls what was feeling off, and he switches Excalibur from his left to right hand. Setsuo begins to charge his final attack on Arthur, but before he could fire it, Arthur swoops in rapidly, splitting Setsuo in half with Violet Flash, killing the Infernal quickly and gracefully.

Etymology

 * The name Setsuo means "section, period, verse, melody" (節) (setsu) and "male, man" (男) (o).
 * Setsuo's surname Miyamoto means "temple, shrine, palace" (宮) (miya) and "base, root, origin, source" (本) (moto).