Astral Buddy Arc

The Astral Buddy Arc (アストラル・バディ編) is the story arc covered in Toaru Kagaku no Railgun: Astral Buddy.

Clone Dolly Ideal
Ideal is the third laboratory under Clone Dolly. Here, test subjects are said to undergo development with aims to develop Level 5s such as Shokuhou Misaki. However, the actual truth behind the facility is that the development of each test subject is dependent on data found within the Parameter List and that Level 5 was never the objective. Notable test subjects included Yumiya Rakko, Yumiya Iruka, Mitsuari Ayu, Hokaze Junko. Another test subject, Yuuri Senya, was under the supervision of a researcher named Toomine Kanari due to the girl's illness.

As Ideal's financial budget became limited, the facility decided to let go of one of their test subjects, to which Mitsuari Ayu volunteered. During this time, Ideal received a proposal for a portable way to manipulate an esper's ability by using another esper's personal reality, with aims to create the ideal esper ability (this would be the precursor to the Indian Poker cards). The lynchpin to this latest experiment would be Yuuri Senya, who can isolate her AIM diffusion field and can thus be used to affect the diffusion fields of other espers. Toomine volunteered to lead the experiment due to her experience with taking care of Senya, but even she had worries about the potential of the experiment going out of control.

Exactly as Toomine anticipated, the experiment went haywire, causing many of the researchers to lose their lives in the initial chaos caused by the rampant diffusion fields and injuring many others. Toomine herself was injured and received a fatal attack from one of the researchers controlled by the diffusion field rampage. The incident eventually reached Kihara Noukan, who warned about the loss of innocent lives in his experiment, and the funding of the facility was cut by a Board member who was actually in contact with Shokuhou Misaki, who knew that Shundou Toshizou, who also led the failed experiment, also used Exterior for his own goals.

Recent Events
The clique led by Shokuhou Misaki, one of two Level 5 s in Tokiwadai Middle School, is the largest student faction in the school. As of late September, several incidents involved eight members of the clique and three non-members, although they are collectively known as a "serial prank" as they are mostly harmless. The incidents were nonetheless escalated to Judgment by Shokuhou herself, represented by her #2 member Hokaze Junko. Based on the investigation of Makigami Komaki and Shirai Kuroko, a "ghost" was said to be the culprit of those incidents, and a peculiar detail in each incident is a note saying "Stay away from my Onee-sama!". With Junko identifying each victim as related to her in some way, both Kuroko and Komaki suspected that she is the "Onee-sama" stated in the note. The two members of Judgment soon fully commit to the case when a latest incident had involved the minor injury of a victim.

Meanwhile, Misaki is continuing her independent investigation on the Indian Poker cards. Although acknowledging that the cards are like "a silly toy", she also recognizes the darker potential in their use, identifying its function to be like brainwashing and the possibility to be used to rewrite a person's personality.

The Ghost Girl of Tokiwadai
Shirai Kuroko of Judgment accepted a request from Hokaze Junko of Tokiwadai Middle School's Shokuhou clique to investigate rumors of a "white shadow" doing pranks on those who are close to her. The latest of such pranks involved someone injured, and so Kuroko became more serious about the case. However, to capture the culprit, Kuroko had to be a viable target of those pranks. Not long after being seen close to Junko, Kuroko receives an ink-filled balloon to the face.

Although lacking a good lead to the perpetrator, Junko's use of her esper ability brought them to a doll filled with perfume and a student from Tokiwadai who admires Junko. At the rooftop, after her feelings were turned down by Junko (who does not have a good grasp of what love is), the admirer slips and falls off the rooftop, narrowly escaping harm with the help of Junko and Kuroko.

With the secret admirer case solved, Junko returned alone to the doll they discovered earlier, only to be surprised that an actual ghost emerged inside of it. Junko would later spend the next few days being possessed by the ghost. One particular day, the ghost girl revealed that she wanted to ask for help in investigating what happened to her and her memories, and Junko agreed to help.

Rescuing Shokuhou Misaki
While the Shokuhou clique tackled an incident involving Shokuhou Misaki's bag being taken by a lemur, Junko planned to keep her agreement with the ghost girl a private matter. However, Misaki urged Junko to tell her problems as part of her vow as clique member. Upon learning of her plight, Misaki used her powers to help Junko make progress on the case of the ghost girl by taking a Tokiwadai student's accurate drawing of the ghost girl. A later visit by Junko to the Judgment 177 Branch Office allowed her to meet Saten Ruiko and Uiharu Kazari who agreed to help in her case.

After the clique successfully captured the lemur that stole Misaki's bag, a plan to track down the culprit by using the lemur was put in place. However, Misaki was unaware that it was a trap set by Yumiya Iruka and her accomplice. Makigami Komaki, who was on patrol nearby, responded to the incident and quickly confronted Misaki's attackers, only to be taken down by the accomplice's combat ability. Komaki managed to contact Junko during the clash, allowing her to fight the two attackers in Komaki's stead, but despite being close to defeating Iruka's accomplice, Junko was caught in a trap and helplessly watched as Misaki was taken by the two. Through the uplifting words of fellow clique member Kobayashi Satori, Junko temporarily assumed leadership of the Shokuhou clique to initiate a plan to rescue the Queen.

The ghost girl managed to locate Misaki and possess her, freeing Misaki from the effects of the "malicious Indian Poker card" used on her. She then contacted Junko, enabling her to locate Misaki within School District 10. While possessing Misaki, the ghost girl tapped into the memories of being within one of the Clone Dolly facilities, Ideal. Here, she saw Mitsuari Ayu and the Yumiya siblings Rakko and Iruka. She also saw how Misaki cured the cluster headaches Junko experienced as a result of her esper ability development. However, what baffled the ghost girl is that she did not know whose memories she was accessing.

Junko soon arrived at Misaki's location, where Iruka waited for her alone with Misaki's phone. Before a fight could happen, Iruka evaded Junko's question about her motivations and instead urged for a fight to the to happen between them. With direct combat proving difficult, Junko switched to strategically weakening Iruka's strong points using water and she overwhelmed Iruka by overcoming the light flash she used on Misaki by using her esper ability. Iruka managed to get up again and used a "sacrificial" tactic by overloading her artificial right eye and using her esper ability to cover the entire area with light beams. Junko managed to withstand the hits from Iruka's powerful attack and quickly tended to her opponent after recovering from her wounds.

Birth of a New Legend
After the successful rescue of Shokuhou Misaki, she and Judgment began to look into the people involved in the attack against the Queen of Tokiwadai. While Komaki and Kuroko linked the attacks to "something" that manipulated then into attacking members of the clique, Misaki was certain that an Indian Poker card was used on Iruka, motivating her to attack Junko. She also knew that her accomplice, Houjou Arei, had no intention of hurting her, and even suspected that she was covering for her. As Misaki surprised Iruka by allowing her to speak her mind to Junko, Arei had her own surprise: she showed footage of Junko using her powers to the public, hoping that it will give birth to "a new Academy City legend" as what her client wished.

Junko was soon visited by the Rank 7 Level 5, Sogiita Gunha, who was looking for information about "a violent student from Tokiwadai" who was said to be responsible for a "gutless" things that were happening. Mistaking Junko for Arei, a fight broke out between Gunha and Junko. This fight is eventually interrupted by Misaki and Kuroko, although Gunha managed to snap out of Misaki's ability on his own. After the clash had somehow formed a bond between Junko and Gunha, the Rank 7 Level 5 agreed to answer questions from both Misaki and Kuroko. Meanwhile, the ghost girl revealed to Junko that she was someone from her distant past who knows about her experiences thus far.

Shortly after the intimate exchange between Junko and the ghost girl, a phenomenon resembling a dark vortex emerged near them, and the ghost girl was taken away by the vortex after she shielded Junko from the attack. With the ghost girl's fate uncertain, Misaki agreed to use the strength of the whole clique to help Junko while she tries to locate the ghost girl's unconscious body.

Search for Yuuri Senya
After learning of how Gunha can perceive changes in persons who are affected by a malicious Indian Poker card that was circulated in the city, Gunha was asked by Kuroko to help in locating those affected. Judgment then handled the apprehension of such people, which were then gathered at a single place. Misaki, who was already aware of the involvement of Indian Poker cards to set up a "composite power" around a girl named Yuuri Senya, eventually identified a convergence point of such powers in the former location of Ideal. After fully recovering from her fight against her, Iruka decided to join forces with Junko in the attack at the facility.

Kuroko and Misaki soon survived an ambush by Houjou Arei, and Kuroko managed to outlast Arei, whose bodily damage received from previous clashes had overwhelmed her countermeasures. Meanwhile, Junko and Iruka managed to reach further into the facility due to Gunha deciding to face Houjou Seigo, Arei's older brother and accomplice to the mastermind Mitsuari Ayu who plans to use Yuuri Senya to revive the failed experiment in the facility. Iruka also left behind Junko to fend off the security robots in the facility.

Junko reached the room where the body of the "ghost girl" Yuuri Senya is secured, and the ghost girl prepared to bid farewell to her friend, knowing that there is no way to save both Senya and the ghost girl. Meanwhile, Misaki contributed in stabilizing the phenomenon gathering in Ideal by weakening Mitsuari's social media influence that created rumors of a "ghost" making contact with people through Indian Poker cards. Upon reaching Ideal, Misaki joined Junko to tell her that they can spend the remaining powers in Ideal for Senya's sake.

Aftermath
Houjou Seigo was defeated by Gunha who agreed to follow his last request to be taken outside of the facility with Mitsuari Ayu. At this point, some of Seigo's organs had shut down and not even Rampage Dress, which he tapped from Junko through Senya's ability Astral Buddy, can be used to regenerate them. Knowing that his is imminent, he forgave Mitsuari for whatever wrongdoings she did and will do, and assured her that she had been a brave person for living  thus far. Seigo died shortly after, unable to hear the words that Mitsuari wanted to say to him at that moment.

Not long after the shutdown of Mitsuari's plan to revive the failed experiment in Ideal, Yuuri Senya began her recovery with Junko and Misaki by her side. Senya then visited the grave of Toomine Kanari for the first time. Meanwhile, Houjou Arei escaped from being confined at a hospital, something that shocked Iruka as Arei was in no shape to be able to make an escape. Regardless, she was certain that they would see each other again.