Battle Royale Arc

The Battle Royale Arc is a major story arc of Toaru Majutsu no Index. Occuring on October 9 of the current year of the timeline on Academy City's Independence day, five factions from the Dark Side of Academy City try to subvert each other in order to attain their goals due to the weakened security of the city, and the effects on their actions on a few point-of-view characters.

It is the second story arc that is part of the Dark Side of Academy City story cycle, which in turn is part of the larger God's Right Seat Arc. The story once again focuses on Accelerator in his continuing struggle against the Dark Side of Academy City, and his development as a protagonist with a nature in contrast to that of Kamijou Touma. It also marks the debut of Hamazura Shiage, minor antagonist from the Skill-Out Uprising, as a protagonist with half of the story focusing on his development from a lackey for ITEM to a protagonist. It is currently the only Toaru Majutsu no Index story arc where Kamijou Touma doesn't appear physically, though in spite of this his influence looms large over both Accelerator Hamazura Shiage.

Background
Far away from the City of Science, Academy City has been making enemies and have allowed the sides in war to be drawn, with Academy City allied to the Anglican Church, while the Roman Catholic Church allied to the Russian Orthodox Church.

Busy with the preparations for War after the events of the 0930 Incident, Academy City's strengthened their defenses against outside forces but the defenses within the city has considerably weakened. This is exacerbated by Academy City sending Powered Suits to attack Avignon and then search for Terra of the Left's corpse. Because of this, a few organizations that up until that point worked for Academy City have broken free from their handlers, who are left powerless due to the Powered Suits they command being used in Avignon, and have started their plans of rebellion against the city.

SCHOOL and ITEM conflict
Kakine Teitoku, apparently aware of Aleister's plans and was distasteful of him being the Spare Plan to Accelerator, likely took over SCHOOL with the intention of forcing Aleister to negotiate with him. Becoming aware of the UNDER_LINE and the secrets that is held within it, Teitoku opted to steal the Tweezers in order to see into it. However, he had a back-up plan that would force Aleister to give him audience, which is killing the main plan, Accelerator. It is likely that he was the one that lead SCHOOL to rebel, severing contact from their liaison.

For his main plan to work he hires a sniper for the purpose of assassinating Oyafune Monaka to create disarray in the Elementary Particle Engineering Laboratory, where the Tweezers are kept. However, on October 6, their sniper is killed by ITEM, forcing them to go to Management to cover up their shortcomings to get them a sniper and arrange the assassination of Monaka. Sunazara Chimitsu is later hired for SCHOOL to replace SCHOOL's sniper and 10 hours or so prior to the events of the arc he deals with Chimitsu and acquires him a MSR-001 sniper rifle, it is likely that he has already given the assassination plans to SCHOOL at this point.

ITEM continues to do their jobs and remains loyal to Academy City. For ITEM's part, their killing of SCHOOL's sniper served as a "warning" for them. Despite this however they did not debate why they targeted Monaka, someone who had low value even amongst the Board of Directors. This unfinished business sets up the stage for the two organizations' conflict in the arc.

Meanwhile, Hamazura Shiage after his defeat Kamijou Touma, leaves Komaba Ritoku's Skill-Out faction under the belief he ruined it as well as the fact that he didn't want to face punishment. He later joins up with ITEM's subordinate organization and somehow ends up being assigned to deal with the girls directly.

BLOCK
Saku Tatsuhiko and the other members of BLOCK already having animosity towards Aleister Crowley become emboldened by the events of the 0930 incident, and with the growing chaos of the world that would lead to War, saw that they could challenge his will. He successfully manage to take control of the organization including its subordinate group from the BLOCK liaison and somehow managed to hire 5,000 mercenaries from the outside of Academy City. Their plan was to storm the Reformatory using the mercenaries and take hostage of Musujime Awaki's comrades that have been kept there as a leverage to force her to cooperate with them regarding the secrets of the Windowless Building, Aleister Crowley's base, which would then, if successful, allow them to execute their masterstroke, transport a Synchronous Multilayer Bomb into the building itself and assassinating him. It is implied that BLOCK used Management as well.

MEMBER
MEMBER remains loyal to Academy City, specifically to that of Aleister Crowley, fitting to them being called his dogs. Xochitl, a member of the organization whose first mission started back in September, was a magician from the magic cabal Return of the Winged One. Her status as a magician is known to the Professor. Due to some extraneous circumstances relating to her cabal, she has her body merged with an original grimoire and is then sent out to deal with Etzali of GROUP, currently using Unabara Mitsuki's appearance after he defected.

GROUP
GROUP remains loyal to the city and do missions for them though only because they are coerced in doing so because of the threat of reprisal on the people the care about. Meanwhile, Accelerator, who was part of the plan during the invasion of Avignon likely to ensure the elimination of Terra of the Left or the Document of Constantine, apparently realized that he could make up for the weaknesses of his choker-style electrode, and opted to take the plans for it from the Heaven Canceller.