Rats

The Rats are a group of children led by Nejiro Kanata who normally congregate in The Pits. However—as Yakumo Amagiri emphasizes—they can be found everywhere, infesting every nook and cranny of the Artificial Island.

Overview
All of the children, most of whom are under fifteen years of age, have been abandoned by their parents or guardians. Though a few individuals attempted to rebel when they first joined the group, these rebels were or would become as 'broken' as the majority: they stopped thinking for themselves, or, more precisely, ceased being able to think for themselves at all. As a consequence, the Rats utterly depend upon Nejiro to tell them what to do and how to survive.

The Rats all dress in shabby grey clothing and possess "empty" eyes. Their emotions appear to be repressed to the point of nonexistence; they know the concept of happiness and desire it, but they do not seem to remember or otherwise know what it feels like. They are desensitized to violence, often placing bets on how long it will take for someone to die. They talk in monotone statements, usually agreeing with one another over simple facts, observations and questions. As Yakumo puts it, the Rats speak in such a way as to be reminiscent of a singular entity rather than a collective of individuals.

Chronology
In 2019, Nejiro (courtesy of Ginga Kanashima) equips the children with 'the Rat': a new small handgun yet to be released to the public. The Rat has poor accuracy, but it is deadly at close range. He plans to use the Rats to eliminate the executives of the Eastern and Western Districts, a goal Ginga shares, for Nejiro considers the executives the root of the island's evil; moreoever, Nejiro wishes for the island itself to be destroyed.

It is revealed that Nejiro is working for the Western District during the Rats' murders of eight Western executives. When the Rats are given their final mission—to attack the Eastern District's casino—Nejiro secretly warns the Eastern District in advance and 'sells them' both the Rats and his contract with the Western District.

The casino incident thus sees the Rats—sans Nejiro—swarm the casino interior to aim their handguns at Gitarin, his human shields, and the other executives. To the children's surprise, their guns do not fire. They are quickly subdued by the Guard Team and others.

In the aftermath, Gitarin or someone else breaks Nejiro's legs in multiple places. Nejiro is found by Yua Kirino, who fetches six Rats to speak with him. From the ensuing conversation, it is clear that the Rats are lost without Nejiro's guidance: their emotions are so repressed that they cannot even feel anger at his betrayal. Nejiro keeps his position as 'king' of the Rats, and he decides to undo the damage he did to the Rats by teaching them about hope and emotions once more.

Over the ensuing year, continuing into Summer 2020, the Rats and Yua enter a symbiotic relationship wherein the Rats aid her cartography efforts; her maps prove great help to the Rats in turn.

That summer, Ginga contacts Nejiro and threatens to kill some of the children if the Rats do not do as he says. Under Ginga's bidding, armed once more, Nejiro and the Rats install bombs on the engine in the island's engine room. Essentially, Gitarin takes the Rats' 'home' hostage in order to give orders to Nejiro. When Gitarin catches wind of the situation, he does the opposite: he takes Nejiro hostage to command the other Rats. The Rats are accordingly instructed on what to do in the engine room by Gitarin.

Later in the engine room, the Rats witness Charlotte and Sherlock Liverpool threatened by Lihuang and Lilei Ei, with Jun Sahara attempting to stop the Ei siblings. When Ginga arrives, he is surprised when the Rats aim their handguns and bow-guns at him. However, the Rats ultimately do not have to take further action.

Trivia

 * One member of the Rats is a Spring-Heeled Joplin.
 * In 2021, the Rats get into trouble in the Western District alongside the Iizuka children. The details of this incident may come to light should a second volume of short stories ever be published.