Setsuo Miyamoto

is a former firefighter, who was turned into a Flame Human. Through the process of the Human Body Ignition Phenomenon, he was able to keep his consciousness, making him a sentient Flame Human.

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 the man fell under the Human Body Ignition Phenomenon, his skin turned dark and parts of his face, above his cheeks, disappeared, leaving a vertical lining above his mouth serving as his eyesight. He has no scalp and flames are present at the back of his head. Setsuo has a very muscular physique and wears white trousers with black shoes. The majority of his facial features are composed of his mouth, though he has no lips and his large teeth are always visible. Through the transformation, the handcuffs he was wearing turned into flames alongside him, which he uses for combat. During his encounter with the 8th Special Fire Brigade, 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.

Personality
As a human, Setsuo appeared to be a troubled and psychologically disturbed man, and was dubbed insane after becoming a serial killer. Setsuo has no concern for the well-being of others, as he recklessly directed his flames and burned two people, and displays ill intent. As a Flame Human, Setsuo retains his psychotic behaviour to an extent and becomes driven with killing everyone in sight, bringing them painful death in the process. Though he possesses a strong killing-intent, as he was able to keep his consciousness, he thinks 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 values his life dearly. Setsuo has shown to have a strong opinion on Special Fire Brigades themselves, comparing them to murderers. As Setsuo kept his sentience after his transformation, he considers himself a life form just as important as human beings. He is willing to deceive others in order to achieve his goals.

Abilities
Setsuo transformed into a Flame Human while having a strong attachment to his life and, as a result, he has a notably strong consciousness and self-awareness. Using the flames around his wrists and from his head, he is able to fly and launch large fireballs. Setsuo can also use the flaming handcuffs as malleable flames to suffocate opponents or use them for offensive attacks. He has a fit physique and has shown to be able to punch through Pusupusu Comet☆ with ease.

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 insanity.

Introduction arc
On the final day of his trial, Setsuo is deemed not guilty for the actions he had done in the past, by reasons of insanity. As he leaves the court, Setsuo begins turning into a Flame Human. 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 Flame Human 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 Flame Human 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 an 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 Flame Human attempts to attack him, but looses his right forearm in the process. Afterwards, Princess Hibana arrives to intercept Shinra's finishing blow, saving Setsuo from jeopardy.

VS 5th Special Fire Brigade arc
Princess Hibana orders her brigade to capture Setsuo in hope of studying him in the future. After the confrontation of the 5th and 8th, Setsuo was brought back to the headquarters of the 5th Brigade, and was violently experimented on by Princess Hibana. During the experimentation, to which Setsuo pleaded for her to stop, he exclaimed that something was going to come out of him if she carried on.