Red Circus

The Red Circus (赤い サーカス) is an extremist group of terrorists in Ostania that hijacked two Eden Academy buses on the way to the Berlint Museum for a field trip. They are the titular main antagonists of the Red Circus Arc.

History
According to their leader, Billy Squire, the Red Circus started as a student movement advocating for peace and equality and spoke out to protect the weakest members of society. They were a respectable movement that fought for their cause with respectable means, but the state turned violent against them and made orders to eliminate the group. Among the killed members was Billy's daughter, Biddy. Due to Billy's connection to Biddy, he became marked by the State Security Service, and with the Red Circus' help, he fled Ostania. Later, he would eventually become the organization's leader.

Imperial Scholars Mixer Arc
Over time, the Red Circus became an organization that sought revenge and justice against the government that wronged them. This also resulted in the group becoming violent, with a news report describing them as "a radical terrorist group... responsible for multiple acts of indiscriminate domestic terrorism." They caught the attention of the assassin group Garden, who dispatched the Thorn Princess to one of their hideouts to kill the men there. The sole survivor of the massacre later encountered the assassin during his day job and attempted to avenge his comrades, but was thwarted by a disguised Anya Forger and decided to live a normal life.

Red Circus Arc
Some time beforehand, the SSS captured 17 of their members, and Billy left Ostania to go into hiding. To have his comrades released and to find safe haven in the nation of Nortica, Billy and the remnants of the Red Circus returned to Ostania, leading a faction in Berlint. Learning that Eden Academy's first-year students will be taking a field trip to the museum, the terrorists plot to kidnap the children and use them as hostages to negotiate with the government to fulfill their goal.

The Red Circus decides to hijack two of the four buses. In Billy's group, one of their members Vadim assumes the role of one of the bus drivers while another group led by Bruce prepare to hijack the other. Things go as planned, as both buses are stolen from the caravan with little resistance. As Billy and his group drive off to Papier Palace Park for the negotiations, Bruce hides the other bus at a warehouse in Demforest District and waits for further orders. During this time, some of their associates gather at Papier Park to await their arrival.

Billy keeps the children quiet by threatening their lives, then explains their goal to them. The group keeps silent about their destination, but Anya, who is among the hostages, figures it out through her telepathy. She and her friend, Becky Blackbell, create an SOS message detailing their destination. While their classmate Damian Desmond distracts the adults, Anya throws the message out the window. Billy realizes what she has done and places a bomb on Anya's neck, then tells the children he will detonate it if they act against them again. However, after seeing how terrified Anya is for her life, Billy reveals in his thoughts that the bomb is fake, unknowingly relieving the girl once she learns this. Damian attempts to persuade Billy to place the bomb on him instead, only for Billy to place another fake bomb on him as well.

Not long afterward, the bus is stopped by the city police, who had received the SOS and laid spike strips down their route. The bus is quickly surrounded by the police, and with the SSS approaching, Billy gets backed into a corner. Billy has the children cover the bus windows and leaves the bus holding Damian as his hostage. Billy states his demands to have his comrades released and secure the group a safe passage to Nortica, promising to free five students for each freed comrade. After making these demands, Billy returns to the bus, where Vadim argues that Billy should have given a deadline, but Billy points out that it will cause the SSS to storm the bus, leaving their only option to stall for time and wait until the government makes a move.

Noticing some of the children needing to go to the bathroom, Billy allows one student at a time to relieve themselves outside. At sundown, the government is in the process of freeing a Red Circus member, and the police request to let the hostages have food and water while they wait. Billy allows this on the condition that someone from Eden Academy delivers it. Henry Henderson, a teacher of most of the students on the bus, volunteers. Inside the bus, Henry sees the state of the injured tutor and demands that he be let go for medical treatment, offering himself to be taken in his place. Billy agrees to this, and Henry joins the hostages. While the children have the rations, Henry notices Billy looking at them with a nostalgic expression and, after learning that he has a daughter, attempts to appeal to his parental sympathies to free them. However, Billy explains that his daughter was killed by the state and remains firm on giving them payback.

As nighttime approaches, the impatient Vadim suggests contacting Bruce to get moving with the second bus. Billy refuses and says they are avoiding doing so to not reveal his location, as Bruce's hostages are now their trump card. However, Yuri Briar of the SSS (and Anya's uncle) manages to locate Bruce and the other bus and, together with a squad, eliminates the members and frees the bus. The SSS shares the news with the Red Circus members and orders them to surrender if they do not wish to meet their comrades' fates. Vadim attempts to motivate Billy to keep going, but Billy is too shaken by the news. Vadim decides to take matters into his own hands and plans to blow up the bus once the SSS storms them.

Anya, who overhears Vadim's plan and an SSS guard regiment preparing to storm the bus, confronts Billy. Having seen Billy's memories of his daughter, she repeats the words Biddy had said to him, which messes with Billy's head. Losing his resolve, Billy removes the bomb from Anya and attempts to free her from the bus, which she refuses. Anya starts demanding more rations, making Billy think that since he left Ostania, the country's economy collapsed so badly that even Eden Academy's upper-class students have been starving. Billy asks Anya why she is doing this, to which she answers: "To make a world where kids don't need to cry," which Billy finds noble. Having enough of their nonsense, Vadim threatens to shoot Anya and urges Billy to avenge his daughter.

Billy remembers the values he taught Biddy in the past, and wanting to redeem himself as a father to the daughter he now sees in Anya, picks up the group's bags and exits the bus. Then, to the shock of everyone, he surrenders to the police and marks himself as the sole planner of their operation, asking them to be lenient with his comrades. Unwilling to accept this outcome, Vadim attempts to drive away but is stopped by the police. Vadim leaves the bus with Anya as his hostage, but before the Secret Police can shoot them both down, Martha Marriott intervenes and immobilizes Vadim with a taser. As the hostages are freed from the bus, the three Red Circus members are taken into custody by the police, and their fates are left unknown.

Trivia

 * The Red Circus is a leftist, possibly communist, group. Besides the "Red" in their name being associated with socialism and communism, in non-English versions of Chapter 69, the SSS Boss describes them as a far-left group. In later chapters of the Red Circus arc, Billy Squire mentions that their ideology is all about equality. He also has disdain for the upper class, including Eden Academy students and their parents, deeming them selfish people.