Fire-breathing Bug

Fire-breathing Bug (火吹き蟲 hifuki mushi) is a "troublemaker"-classed collective of people responsible for multiple acts of arson and murder in Shinjuku spanning one hundred years. As a collective, Bug maintains the belief that anyone or anything connected to the Other Side of the Sky is a "bug" in Earth's system that necessitates extermination, 'itself' or 'themselves' included; in the meantime, Bug has an especiall vendetta against the Bastard Children of Sabaramond, an organization with whom Bug has a century-old vendetta for its practice of experimenting on human children.

At the scene of their crimes, they leave the following message as their calling card: "This world is a buggy program," followed by a second half that varies depending on the context. Only the first half—"This world is a buggy program"—is known to and publicized by the media, as Comps-3 has kept the second part secret during its investigation into Fire-breathing Bug.

Collective

 * Identifying Factors

The individuals—hereafter referred to as "Bugs"—who constitute Fire-breathing Bug have no commonalities in ethnicity, gender, age, class, profession, or other demographic criteria. The primary signal that identifies or unites Bugs is their slogan 「火の用心」 (hinoyōjin, meaning "watch out for fires"), as emblazoned on various forms of rain gear: although dark umbrellas are their signature accessory, a raincoat with the slogan on its back has been an identifier for at least one bug. Caution must be taken before associating all rain appurtenance with all Bugs, as not all may be wearing 'branded' rain paraphenelia, and it is meanwhile only natural for the masses to don rain gear when it rains; moreover, there is no guarantee that Bugs will be able or choose to have rain gear on their persons when they are acting in the collective's name.

An assembly of umbrella-carrying Bugs, when looked upon from a bird's eye-view, resembles a swarm of black insects.

in revision.
 * Traits and Worldview

Modus Operandi
In lieu of actually breathing fire, Fire-breathing Bugs wield various types of emitters in order to remotely ignite their target. What exactly these emitters 'emit' is unknown (theories include electromagnetic waves and lasers), but the execution as theorized by Tsubaki Iwanome is as follows: like how gamma rays are used in Gamma Knife radiosurgery, all the Bugs point their emitters at their target; whatever is at the point of the "rays'" intersection will be burned.

Such technology appears to work over a considerable distance and can achieve highly precise results, given that a keen degree of accuracy would be needed by all participants to burn legible letters into remote targets.

Recent developments suggest that Bugs are recipients of brainwashing, and that the manner of brainwashing has to do with songs. It is increasingly evident that Fire-breathing Bug's penchant for singing Japanese children's folk songs is no mere penchant, but an active factor in 'controlling' or 'influencing' Bugs.

Chronology
To be added.

Notable Bugs

 * Mitsu Haigawara and Takajirou Toura (two key founders)
 * The slim, suit-wearing individual who was the first Bug to speak with Sorimura in person, who was seen at Know's murder, and who spoke with Corpse God via cell phone from the stairwell.
 * It is possible that Bug was a different person in each indicated scene, but there has been no given reason to assume otherwise.
 * The raincoat-wearing teenage girl who had her fortune read at the Fortuneteller Shop, and later monitors the Great Shinjuku War.

Trivia

 * The Fire-breathing Bug's name is first mentioned at the end of Chapter 5, twelve chapters before his formal debut.