Group

GROUP (グループ) is an Academy City-based underground organization. They are composed of four main field operatrives: Tsuchimikado Motoharu, Accelerator, Etzali (disguised as Unabara Mitsuki), and Musujime Awaki. The organization is referred to as "a small group that exists in the underworld, working to defend the mainstream society." GROUP is referenced during the invasion of Academy City where Accelerator becomes its newest recruit. They are later properly introduced during the Skill-Out uprising to deal with Komaba Ritoku's troublesome plans against the city.

Although much of their appearance has them act on the orders of the higher-ups of the city. they chafe under the yoke of the Dark Side of Academy City and the higher-ups that control them. The faction often works behind the backs of their superiors in order to undermine them and eventually free themselves from their control.

After the events of World War III, the organization is disbanded, succeeding in their desires to be free from the city's control. The organizations becomes the only known faction from the Dark Side of Academy City that fought in the factional war on October 9 to have all its field operatives survive.

Principles
Like the other Dark Side of Academy City factions their level of security and authority are the same—an unofficial unit created by putting few persons together. Their primary purpose is to take Academy City's Dark Side, similar to ITEM, and more often than not, perform illegal acts for Academy City. GROUP was formed to take care of internal affairs of Academy City's Dark Side, and is one of the more successful organizations. After the events of October 9, GROUP remains the only underground organisation that remains intact out of the five that were shown in the story.

The four field operatives are composed of espers and magicians blackmailed in some way to join and keep them in the organization, as such they are coerced to work together for the sake of their mission in order to protect something important to them. GROUP is referred to as a "cold-hearted" group, with the standard idea within the organization is that each member had to deal with their own problems. This exemplified by the three field operatives leaving Etzali to his fate and not determined to rescue him from BLOCK during the course of their missions in October 9.

After joining the organization, members are supposed to follow rules set-out by the GROUP liaison, and can apparently be individually used for a mission if it needs be. The field members are provided with transportation to their mission if they so desire, but as well as information, and technology provided by the technical team. It is likely that much of what the members doesn't matter as long as they finish the mission, though the liaison can call them out if they go overboard, as shown when he berates Accelerator after he tears Kakine Teitoku apart in front of a large crowd. GROUP members are are apparently recommended to stay in the building known as the "Nap Room," though this isn't required as they are allowed to have their own living quarters.

Despite this, it is implied that there is no way out of the organization other than dying. Motoharu says to Accelerator that if he followed the rules laid out by the Board of Directors then they will not let him out. He says that the organization is made so they profit no matter what happens.

Organization
There are four core members of the organization who does the the field work during missions, composed of powerful and skilled Espers and Magicians. Although they seem to have no official leader, and operate based on individual decisions, Tsuchimikado Motoharu is the one who actively gives orders, requests, and even advises other members during missions. Even Accelerator once referred to him as "senpai," as a reference to his seniority. They do however, take orders from the GROUP liaison, also known as the Man on the Phone, though Accelerator seems to be contacted by their backer more often than the others, he in turn, takes orders from the higher-ups.

Along with the four, the organization is supported by a large subordinate organization. They do things for the organization from menial labor such as transporting prisoners, corpses (including members of the field operatives), and even the team, to complex background work such as the technical department which supports the organization by giving the members useful technical aid. The organization is also composed of telepath-type espers and Powered Suit operatives.

As with SCHOOL's example, the team is also likely able to accompany them in missions if they wanted to.

Field operatives

 * Tsuchimikado Motoharu
 * Accelerator
 * Musujime Awaki
 * Etzali under the guise of Unabara Mitsuki

Toaru Majutsu no Index
Prior to the formation of the four field operatives becoming part of GROUP, a few of its member have already met. Etzali met Tsuchimikado Motoharu after Kamijou Touma defeated him and called Motoharu to deal with the magician, while Accelerator met Musujime Awaki when she attempted to revive the Tree Diagram using the Remnant and rousing the anger of Accelerator as there was a potential that the Sisters would be in danger.

Skill-Out Uprising
Due to Academy City currently fortifying its anti-Roman Catholic battle lines, the defense on the inside has gotten thinner. GROUP was given a job to do a clean sweep of a force that is going to use that gap in the defences to do some damage to the functionality of Academy City.

Battle Royale Arc
October 9.

Tsuchimikado Motoharu met Management inside his closet disguised office inside a department store, he posed as a client to gain entry and catch him. Meanwhile, Accelerator asked the electrode designs from Heaven Canceller at gunpoint, to which the latter complied. Motoharu then had Etzali search Management's apartment for information on contacts and business deals. While Mitsuki was doing the investigation, the apartment was raided by a group of black-clad men apparently destroying the information that GROUP is after. In the aftermath of BLOCK raiding the apartment worried about Management's information getting obtained by another dark side organization, Motoharu then showed that he was aware of Etzali's true identity and power and realized that in the confusion he had infiltrated BLOCK when they found Yamate's corpse and give an explanation to Accelerator and Awaki. After using a reader to scan the chips that Etzali found in the apartment, they found out that he was used to hire Sunazara Chimitsu and realized that the target was Oyafune Monaka. While searching for Chimitsu, Motoharu and Accelerator saw Last Order asking Uiharu Kazari for help looking for Accelerator, much to his annoyance and Motoharu's amusement until he spotted Maika in the crowd as well. Suddenly the Wind Defense nearby turned off they realized that it had been done with Chimitsu's Magnetic Sniper Riffle. After the failed attack thanks to Accelerator they found the hotel room that Chimitsu had fired from already abandoned when Accelerator informs him by phone that his employer is a rival group SCHOOL.

Later they discover that other organizations existed similar to theirs and were in motion and wonder which ones were involved with the destruction of Management's apartment, the attack on the paddy wagon, which one Etzali was concealing himself a part of and why did SCHOOL try to assassinate Oyafune Monaka. Shortly thereafter they received information that District 5’s Virus Isolation Center was being hacked while Accelerator protest at being sent to deal with this, Motoharu states that the culprits are most likely one of the other groups and that they have betrayed Academy City and began to move. While heading to District 7, they received information that a satellite control center is under electronic attack and then concluded that some other group is trying to split them up and used the Virus Isolation Center as a decoy. Accelerator then decides to head to District 23 despite Motoharu's protests and goes in order to prevent Hikoboshi II from being used as a weapon. He then contacted Anti-Skill to ask information about the satellite but the "man on the phone" who usually gives instructions to GROUP interrupted so Accelerator asked him instead. After the conversation with the "man on the phone," his phone began ringing again, and this time, it was Mitsuki who just informed him that SCHOOL is not the one who is hacking the satellite but BLOCK, the group where he disguises. It turns out that the satellite will be used to attack District 13.

On the way, Accelerator met someone from yet another group called MEMBER and they fought. Motoharu and Awaki later meet back up with both Accelerator and Etzali after the latter ruined BLOCK's attempt to bring 5000 mercenaries into Academy City. They then argued about the actions of SCHOOL and BLOCK before interrogating one of BLOCK's mercenaries that they captured about their plans whom they learned that their target was the Juvenile Hall in District 10 to take Awaki's comrades as bragging chips to gain entry to the windowless building and then assassinate Aleister Crowley. After their arrival to their destination, they split up again where Etzali stays to fight Xochitl, Accelerator goes to finish off the remaining mercenaries while he and Awaki go off to where her comrades were being held. They the meet the leader of BLOCK Saku Tatsuhiko who then has argument with his second Teshio Megumi on how they would use the hostages ending with Megumi knocking out Saku. Motoharu tries to fight her but is easily overpowered by her experience and own version of Anti-Skill subduing technique. After the fight he asks Awaki if she was alright before they both rejoined the rest of GROUP upstairs. Accelerator then fought with Kakine Teitoku and defeated him. Motoharu who is hiding among the crowd of onlookers recovered the Tweezers. He then shares the purpose of the device and the existence of UNDER_LINE. They decoded data and found information on several things relating to the Battle Royale including the existence of DRAGON.