Jailbreaker Arc

Jailbreaker Arc (編) is a story arc in the Toaru Kagaku no Railgun manga series, covering chapters 98 to 130.

The story focuses on a jailbreak trial organized by the operators of a new private juvenile hall in Academy City in order to test the facility's security features. The challenge is to break into the facility and successfully extract the target prisoner, with a one billion yen reward for successful completion. Various people wish to take advantage of the opportunities presented by this event, both openly and secretly.

Second Reformatory
The new Second Reformatory was the second such facility set to open in Academy City, but unlike the publicly-run Reformatory, this juvenile hall was run by a private security business. It was built in response to a rise in crimes committed by espers as opposed to those involving Skill Outs and a belief that the private firm could provide a better service than the publicly-run facility.

The outer wall is 15m tall and encloses the facility in the shape of a right trapezoid. There are two entrances; the main gate where suspects are brought in and which staff use to go in and out, and a back gate which is normally kept closed and only opened in emergencies. The main gate is the only one which vehicles can pass through. It is apparently 1.8 times as strong as the previous Reformatory's gate and there are two additional shutters of the same strength which can be closed behind it. Wind machines installed in the wall can be used to blow projectiles off course. There are pipes running through the wall, which carry a fast hardening filler known as Birdlime (バードライム) to rapidly seal up any holes made in the wall. There are also sensors and defenses in the wall ducts. In the grounds between the perimeter fence and the outer wall, aside from robots, there are numerous acoustic weapons and adhesive pitfalls.

The prison and holding centers are both located within the walls, with an internal division between the two, so as to keep prisoners under the effects of the jammers while being transported between them. For some cases, trials are held online with the prisoner remaining in the facility throughout.

The juvenile hall has a large complement of guard robots, which come in several varieties:
 * The standard guard robots have a domed body on a crescent-shaped base with three legs and a translucent front covering sensors and circuitry.  A weapon block is located on the left side of the robot, capable of firing impact rounds, electrified nets and liquid shots.  There is also a variant which is equipped with a rubber bullet gatling gun instead. The robots are also equipped with speakers and bar scanners. They can travel along the side of the wall on their base, with their legs folded up behind them.
 * There are larger, bipedal robots, referred to as war armadillos, which are also capable of moving around rolled into a ball. They are equipped with a heat blade and air gun held in arms behind the head, as well as an acoustic weapon housed in the chest. Meant to keep intruders out, they are stationed at the outer wall.
 * Type: Hunting Wasp (タイプ:ハンティングワスプ) (T:HW): Flying riot suppression robots in the shape of wasps, with a stinger which injects a sleeping drug.
 * Type: Giant Centipede (タイプ:ジャイアントセンチピード) (T:GC): A robot in the shape of a giant centipede, which constricts targets to restrain them.
 * The largest of these security robots, referred to as riot suppression gigapedes, are stationed inside the prison buildings. Being a robot operating in the solitary confinement area and well within the jammer range, it is intended to deal with inmates who are unable to safely use their esper abilities.

There are also quadrupedal guide robots within the walls, designed by Kyougoku, which have his face on them and somewhat resemble a.

The Jailbreak Trial
In order to promote the new juvenile hall and test its security features, Director Kyougoku Ryouta invited interested espers to challenge the facility and search out vulnerabilities in a Jailbreak Trial (脱獄トライアル). The objective of the challenge was to break into the facility, find and retrieve a target prisoner (played by one of the jailers and located in the girl's building),  and then break out of the facility with them. The reward for successfully completing the challenge was one billion yen.

The exact victory conditions have been noted to be somewhat vague, likely because the organizers didn't expect anyone to complete the challenge successfully. However the facility's defenses were to operate at combat specs during the event, and competitors had to sign a liability form, stating that the organizers were not responsible for any injuries or death occurring as a result of their participation. The rules state that competitors don't have to use the main gate and if they are using equipment too large to carry, to pick it up from the neighboring parking lot.

During the trial, the actual prisoners were apparently moved to the bottom two levels of the prison building basement, while the test prisoner was positioned alone on the top level of the basement.

During the interview where he announced the jailbreak trial, Kyougoku boasted that his company had built defenses to hold even a Level 5 and that even if the likes of Tokiwadai Middle School gathered all of their students, he doubted they'd even breach the first wall. This prompted several Tokiwadai students to enter, including Misaka Mikoto.

Competitors
The challenge and its rewards attracted 4,378 people from various backgrounds and using a variety of methods to attempt the trial.

Notable competitors include:

Trial
In a livestream posted on a video streaming website, Director Kyougoku Ryouta presented the Second Reformatory as well as the "large-scale event" he is planning to organize to enable participants to find flaws in the facility's security systems. Neither among Misaka Mikoto, Shirai Kuroko, Saten Ruiko and Uiharu Kazari were interested in the event, even with the one billion yen prize. Kuroko was not convinced that the organizer will pay the full prize money, while Mikoto wanted a break from the events that had happened recently. However, Kyougoku provoked the two known Level 5s of Tokiwadai Middle School upon claiming that his facility can hold a Level 5 as well as the school's entire student body. Mikoto responded by participating alongside Kuroko (who joined to keep tabs on her), Saten and Uiharu. Shokuhou Misaki claimed to be unaffected by Kyougoku's taunting, yet allowed Kouzaku Mitori and Dolly to join.

With all participants required to sign a waiver and allowed to bring and store whatever tools that can be used for the jailbreak trial, Uiharu brought a digital floor plan of the facility, while Saten brought a pair of "ninja sucker gloves" that will allow her to scale the walls of the Reformatory.

The Outer Wall
As soon as the signal is given, the many participants begin their attempts to siege the outer wall while the first wave of security robots were deployed to respond to them as if they are escapees from the facility. Many from the first attackers were subdued by the various tools equipped by the security robots, while a bolder attempt led by an armored car brought by a group of ironworks workers was foiled by an acoustic weapon hidden at the facility's surface. Eventually, some participants like Fusou Ayame and a boy in a tanuki mask made their counterattack by destroying some of the opposing machines.

Kuroko quickly helped Mikoto, Saten and Uiharu cross a sticky pitfall ahead of them. Meanwhile, Mitori's attempt to use a drone to sneak into the ducts of the facility was foiled by the presence of security systems inside, and Dolly successfully defends her from an incoming attack from a security robot.

Later on, larger-scale attempts to bring down the outer wall were used by the participants. Kyougoku watches from the control room as his sturdy walls withstood several large explosives and his War Armadillos faced the exoskeletons of a robot club. With the effects of the AIM Jammers within the outer wall area capable of affecting those who try to climb it, Kongou Mitsuko and her posse decided to attack the outer wall from a distance using large logs. Kyougoku remains confident of his security systems and overrules his assistant's suggestion to use the long-ranged AIM Jammers, knowing that his wall can shrug off the attack. True enough, a wind machine within the outer wall threw off the trajectory of Kongou's ejection points, forcing her to stop using her ability on the logs. The first successful attempt came from Mikoto, who used nearby metal debris to create a large projectile for her Railgun, but the damage was quickly covered with Birdlime.

Mikoto suddenly had an idea after seeing how one of Saten's gloves formed an imprint on the ground after being covered in iron sand and water. By enlisting the help of the robot club members, Kongou's Aero Hand and scattered metal debris, Mikoto managed to punch a hole by making a first hole using her Railgun, plugging it with logs before the Birdlime can harden, and firing another Railgun on the logs. Another group, led by Oumi Shuri of the Kouga Ninja, also managed to climb across the outer wall. Although Kyougoku was dumbfounded by the breakthrough, his assistant reminded him that the outer wall complex has many AIM Jammers that can easily restrain esper ability usage.

Inside the Wall
Word of the successful breach leading to the outer wall complex caused a stampede of people to slow down the way inside. During the chaos, Uiharu is separated from Mikoto, Kuroko and Saten who had to flee while being pursued by more security robots. Other people who had managed to enter the outer wall complex were Scavenger, who plans to take advantage of a leading participant to take the winning prize for themselves, Mitori and Dolly, Yamashiro Shoubu, the robot club members, Fusou Ayame, who was incapacitated by a Type: Hunting Wasp robot designed to inject a sleeping agent on its victims, and Oumi Shuri's group. With the help of Yakumaru, who tries to eliminate any threats under Leader's orders, Mikoto's group first reached the Boys' Building by mistake, and had to travel further to reach the Girls' Building.

Prison Building
By the time Mikoto, Kuroko and Saten entered the Girls' Building, there are already multiple people inside. Among them are a girl known for saying "ha wa wa" all the time, Yamashiro Shoubu, Mitori and Dolly, and Oumi Shuri's group, all of which ending up facing the security robots inside one way or another. As Shoubu and the "ha wa wa" girl went together, Shuri decided to split the group into three to improve their chances to obtain information: Sakata and Asai composed one group, while Yasu is accompanied by Tsurigane. Shuri soon encountered Mikoto's group and temporarily joined them with an interest to know more about high-level espers while acting as a vulnerable young participant.

At one point inside the facility, Mikoto and the others meet the "ha wa wa" girl being chased by two riot suppression gigapedes, then joined by a few war armadillos and security robots. Mikoto reveals that the war armadillos and security robots are actually reprogrammed by Mikoto during her last encounter with them, and she used them for her counterattack. She then brought the rest of the robots to the whereabouts of the target, using the war armadillos to cut open doors along the way. They also encountered Kongou's group, who agreed to accompany them to the target's holding cell.

Mikoto and the others were surprised to discover that the holding cell is unlocked and empty, and the control room discovered that the "footage" of the target is fake. Not long after, alarms declaring the end of the jailbreak trial were heard throughout the facility. Elsewhere, Uiharu accompanied the target after her flawless hacking of the Second Reformatory's security systems.

Post-Trial
Although flustered at the idea of his security systems being hacked by a young girl, Director Kyougoku accepted the outcome and officially announced the winner of the Jailbreak Trial. After reuniting with the others, Mikoto revealed that she had a hunch about who opened the doors to the Girls' Building, and Uiharu stated that the one billion yen prize will be donated to Asunaro Park.

At a nearby fair that sells memorabilia of the Jailbreak Trial, Mitori met up with two members of the Shokuhou clique who also joined the event to watch over Dolly. While thinking about the outcome of the event, Mitori found the circumstances that enabled a hacker to win the event to be suspicious. Inside the Second Reformatory, Director Kyougoku confirms the outcome of the jailbreak trial in person and, while bickering with his assistant about who is responsible for the blunder, a mistaken opening of a facility door led him to discover Iizuka, the real target of the jailbreak trial, tied up and locked inside one of the lockers.

As Iizuka is taken to the medical room to recuperate, Kyougoku quickly surmised that only someone from within is responsible for the switch. His assistant Aohoshi eventually showed her true colors and restrained the director with the help of jailers that follow her bidding. Elsewhere, Tsurigane attacks Shuri after dismissing her fellow Kouga ninja and manages to cut her using a knife coated with a numbing agent. Yamashiro Shoubu also falls to the "ha wa wa" girl after revealing that his ability senses a strong sense of malice in her.

Aohoshi, Tsurigane, the "ha wa wa" girl (named Raifu) and the "target" set free earlier met inside an abandoned building. The fourth girl, who manifests the ability to summon a dragon by her side, showed her interest in Uiharu's capabilities.