Fire-breathing Bug

The Fire-Breathing Bug (火吹き蟲 hifuki mushi) is a Shinjuku-based troublemaker who specializes in arson. Per Chapter 51, Fire-Breathing Bug has been confirmed to encompass multiple people and cannot merely be defined as a mere individual.

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.

Appearance
Fire-Breathing Bug upon 'his' introduction debuts as a humanoid individual with a slim, masculine frame outfitted in a business suit; 'his' face is obscured by his umbrella, the outer side of which bears the warning 'Watch out for fires' in kana (火の用心 hinoyōjin). This is the Bug with most appearances to date.

In Chapter 23, the Bug who burns down Yougangumi carries the same or otherwise identical face-obscuring umbrella and wears a suit; however, his frame is noticeably stouter than the first Bug. This Bug is likely one of the men previously shown in the hallway.

The Bug who has her fortune read by Corpse God and later returns to the building is a short-haired brunette girl of high school age, seen both times wearing a raincoat bearing the motto "watch out for fires" on its back over her uniform.

An unknown number of additional Bugs exist in the police force and common citizenry. Rainwear and rain gear are directly associated with Bugs: though umbrellas are the most common example of rain gear seen, raincoats and ponchos have also been spotted.

Personality
An enigmatic figure in many respects, Fire-Breathing Bug is proactive toward goals that have yet to be understood in full. 'He' acts to incinerate those he has deemed 'bugs' or 'pests' and appears to take some satisfaction in doing so, as he is seen singing with a smile while Know burns. On the one hand he is liable to tell someone like Tena Sorimura that they can "fly into the flame for all [he cares]," but on the other he values emotions and appears to have taken severe umbrage with "the bastard children of Sabaramond" for reasons yet to be illuminated.

The Bug often speaks in a slow if not halting tone. 'He' also has a habit of singing Japanese folk songs, especially the children's song Furusato.

Chronology
To be added.

Abilities
In lieu of actually breathing fire, Fire-Breathing Bugs cooperatively carry and use various types of emitters to remotely carry out arson. 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.

Trivia

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