Red Circus

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

History
According to 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 becomes marked by the State Security Service, and with the Red Circus' help, he flees Ostania.

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 eventually caught the attention of the assassin group Garden, who dispatched the Thorn Princess to their hideout to kill everyone there. The sole survivor of the massacre encountered the Thorn Princess during his day job and attempted to exact revenge for his comrades, but was promptly thwarted by a disguised Anya Forger and decided to live a normal life.

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.