Dream Ranker Arc

Dream Ranker Arc (編) is a major story arc in the Toaru Kagaku no Railgun manga and anime.

The story arc is based on the Indian Poker cards, devices that allow people to look into and learn from the dreams of other people, as well as events related to its creator, Kuriba Ryouko, and the inhabitants of Academy City that use, distribute and profit from the cards themselves. The arc is named after the Dream Rankers, people who produce Indian Poker cards.

Dream Ranker Technology
A recent trend among the student population of Academy City involves a set of cards called Indian Poker and related technology that allows a person to capture one's dreams and store it in a card-like form for other people to use. The exact process of making Indian Poker cards is unknown, although diagrams are spread by those experienced in making those cards through the Internet, showing that the machine used in making an Indian Poker card requires several individual pieces of technology.

The fad manages to seep through the Garden of Academy City's  District 7, allowing one of its students to acquire and share her own dreams with others, as well as learn mundane abilities like expertly playing kendama and twirling pens or more noteworthy ones like learning a new language or properly preparing chemicals with a desired effect. The cards are also used to store confidential intelligence in a physical form by certain organizations.

Shared Dreams
During class, Misaka Mikoto and Shokuhou Misaki enter a typical short argument against each other. A third girl involved, who is a third-year member of Misaki's clique, feels responsible for causing the encounter between the two and meets with Mikoto later during the day. Here, as a peace offering, she hands a card to Mikoto. Mikoto does not know anything about the card she received, but her friend Saten Ruiko explains that it is part of a recent trend involving cards used to share dreams with other people. Curious about how the card works, Mikoto uses it that night and ends up in a fairytale land with several Gekota-like characters serving a queen who resembles Shokuhou Misaki herself. In her rage after being dressed as a maid and forced to serve Misaki, she snaps out of her dream.

Although Mikoto loses her interest in learning more about Dream Rankers, she catches wind of more details about them through Saten. She is later invited by the Hokaze Junko to have some tea that afternoon, only to find out that it was the latter's plan to bring the two Level 5s of Tokiwadai closer. The three girls then overhear a conversation nearby involving a Dream Ranker who belongs to the highest rank, known to his patrons as BLAU. Although BLAU claims to share his dreams for free, the sheer amount of indecent content he propagates is enough for Mikoto and Misaki, after hearing that they have both ended up as one of his "targets", the two make a temporary truce in order to deal with him swiftly and destroy any Dream Ranker cards in the possession of BLAU and his companions.

Treasure Hunter App
Elsewhere, in the morning of September 27th, an accident was reported to the authorities. Among those who began an investigation about the event were Judgment's Uiharu Kazari and Shirai Kuroko. Both Uiharu and Kuroko were informed about a particular mobile application which allows users to earn prizes by capturing images of designated areas of the city. The app also tags locations of accidents, whether it has happened before or will happen in the future. In addition to this, the app has a prediction window of twenty to forty minutes (ten to twenty minutes off the indicated time) and is known for its high rate of success.

Kuroko suspects that an esper that uses an ability similar to Precognition may be involved with the app and takes Uiharu to head to a nearby roadside where an accident is predicted to happen. Just as foreseen, an accident involving a truck and a car occurred at the location. Kuroko, however, manages to save a student that was caught in the path of the accident. After confirming that there are no casualties, Kuroko heads to the nearest building with a vantage point of the area as she suspects that the one who made the predictions will be nearby to confirm them. There, she meets Miyama Shaei, an elementary school boy who claims to be the creator of the Treasure Hunter App.

Shaei talks to Kuroko and Uiharu about his ability, which allows him to produce photographs with information about a future event with the use of an instant camera. According to Shaei, his images usually require further analysis through a research institution's equipment, but increasing his focus he can include the date and location of the incident and then analyze the photos with a smartphone app developed by a particular company for Thoughtography espers, the app now used to compile images of predictions made. As of the present, he is using the app not only to conceal his identity but also to look for someone who can overturn the predictions he made, something that he was unable to do alone. Kuroko is skeptical that the nature of her teleportation can counter Shaei's prediction ability, but later agrees to help after seeing his abilities firsthand.

With the help of Kuroko and Uiharu, several of Shaei's predictions are intercepted with positive results. However, the drive to make even more results happen push him to the point where his body starts breaking down due to excessive use of his ability. Nonetheless, as Shaei is admitted to a hospital to recuperate, the Judgment duo continues to work with his predictions. Shaei makes enough progress in his recovery and frantically heads to a nearby park where one particular prediction that involves his dog friend Pero. Here, he was able to witness Kuroko rescue Pero from certain harm.

After Shaei makes a full recovery, he plans to stop using his ability. However, an optimistic Kuroko urges him to follow through the Power Curriculum Program to improve on his ability so that he can use it without causing harm to his body. Shaei also gives Pero to his former classmate Ookawachi Megumi to take care of for the meantime. Judgment, on the other hand, continues investigating on the park fire incident. An interrogation of the students who caused the fire later reveals that they were under the influence of an Indian Poker card that taught them how to cause cherry trees to be in full bloom.

Quest for the Bust Upper
Although initially indifferent about the concept of Indian Poker cards, Mikoto eventually rekindles her interest about the cards when she heard about a certain card that can increase the bust size of anyone who uses it: the infamous Bust Upper. Meanwhile, Kinuhata Saiai is suffering from a looming feeling of jealousy over the breasts of her partners in (to the point that Frenda's breasts are bigger than hers) and this forces her to look for a way to make her bust size grow. This inevitably arranges a meeting between the two girls who want the Bust Upper for themselves. However, due to a mix-up caused by the man selling the Dream Ranker cards, the Bust Upper card is mixed among others that the man is selling. Eventually, Mikoto and Saiai each agree to buy half of all the cards sold by the man, and due to the nature of Indian Poker cards, they also agree to share the Bust Upper card with each other, provided that the card is found among the stockpile of cards in their profession.

In a nearby internet lounge, Saiai and Mikoto spend the time using Indian Poker cards and eventually find themselves in the dreams of various people. Mikoto's dreams include a kunoichi in training, a researcher with a similar plight about bust size, a roadside artist who manages to talk to someone who takes pride in her figure, and a timid high school girl who laments about her C-cup breasts (the anime replaces the latter two dreams with a lady who mistook herself as being scouted for an idol contract and a student of Tokiwadai who remembered her gaffe at the Daihaseisai and her own insecurities) while Kinuhata's dreams include a maid who has to endure her brother's perversions and a kunoichi studying a certain ninja clan's seduction techniques. The frustration caused by the breast-themed encounters cause both girls to lose their tempers to the point that they are evicted from the internet lounge. Mikoto and Saiai later continue their search in the poolside of a nearby resort, where a crow snatches a card from their stockpile, only to drop it on the bench of a random girl in a park after being spooked by a certain nun's cat. The next day, that girl appears with a bigger bust size than before.

Pursuit for the "Chopsticks"
Saten Ruiko is shopping at a grocery when she suddenly finds a blonde girl desperately looking for canned mackerel after she picked up the last two cans on sale. This girl, named Frenda Seivelun, ends up wasting a can after hastily opening the one she received from Saten, and Saten hesitantly decides to invite Frenda after seeing her reach the point of crying after the accident. At Saten's apartment, Frenda enjoys the mackerel curry prepared by Saten despite being a purist about eating mackerel and decides to become friends with her, registering her ID in the social networking service Speech Bubble. Frenda and Saten later use the SNS to talk with each other about random things.

Saten later goes to the peddler of Dream Ranker cards that she patronizes and she is quickly asked if she is interested about some of the cards on sale, including a card from a coin stacking record holder and "someone with amazing skill using chopsticks". Saten appears to purchase the "chopsticks" card, oblivious to the fact that her activities are tracked down by a girl in a dress and a boy wearing a peculiar head accessory, who identify the "chopsticks" mentioned in the Indian Poker card as the Tweezers, a device that can be used to handle microscopic objects. Saten is abducted by thugs shortly after the purchase, and Frenda, who still feels indebted to Saten after the hearty meal, decides to pursue the van that took Saten captive and retrieve her without hurting either the thugs or Saten herself.

As the boy with a head accessory extracts information about an Indian Poker card stored in a secure research facility, a girl from Private Shidarezakura Academy who follows the boy's orders heads to the thugs who have lost what the boy deemed as an important target. Here, the girl, named Yumiya Rakko, identifies the perpetrator of the ambush based on footprints on the ground. Meanwhile, Saten manages to survive the kidnapping, losing only her phone and the Indian Poker card she just bought, but Rakko successfully tracks down Frenda and uses an unknown device to snipe her from a distance in the middle of a bustling crowd.

Frenda manages to escape despite the injury from Rakko's attack and attempts to elude her by using a nearby department store to blend with the bystanders inside. However, Frenda discovers that Rakko not only blends herself with the crowd but can also attack her while in hiding. Frenda decides to use Saten as bait to allow herself to escape, but Saten already had a hunch about being Rakko's target and agrees to split up. Eventually, Frenda decides to team up with Saten, using the assumption that Rakko's target is Saten to lay out explosive traps throughout the department store building. In reality, Rakko's real target is Frenda, but the plan ultimately worked in favor of Frenda and Saten.

Rakko and Frenda start a close-quarters fight inside the department store building, causing panicked customers, as well as Saten, to evacuate the building. Frenda struggles to match Rakko's attacks because of the injuries she received earlier, but she manages to hold out long enough to trigger several thermobaric bombs she planted while Saten is luring out Rakko. The blasts immediately shroud the building with smoke and deplete the oxygen in the area, forcing Rakko to approach a hole caused by the explosions. This, however, was anticipated by Frenda. Using the smoke as cover, Frenda shoves several small bombs into Rakko's mouth and pushes her out of the hole. Then, after saying her "last regards" to Rakko, Frenda throws more bombs to Rakko's direction, consuming the falling girl in a large explosion.

In spite of her exposure to seemingly lethal explosives from the fight against Frenda, Rakko manages to survive with the help of Yobou Banka. But, as a result of the injuries she received, she is wearing an eyepatch over her left eye, as well as an apparatus that covers her nose, neck and lower jaw. As SCHOOL finally tracks down the location of the Tweezers with the help of Indian Poker cards gathered by Banka, in a meeting between the members of SCHOOL, Rakko urges SCHOOL's leader, Kakine Teitoku, to allow her to pursue Frenda once more due to having a strange obsession towards her during their last fight at the mall. Kakine rejects the request after losing patience over Rakko's bickering, causing the latter to storm out. Meanwhile, the Girl in the dress and Kakine both agree that Rakko has already outlived her usefulness. Kakine then tasks the Girl in dress to prepare for the replacement sniper for SCHOOL, regardless of Rakko's response to the situation.

The Doppelganger and the Information Leak Crisis
For the first time, Judgment begins an investigation directly involved with the Indian Poker cards, in response to reports where the cards are used to spread secret information from certain organizations. Judgment responds to the issue by trying to control the production of Indian Poker cards. However, diagrams that show the devices required to make a machine that produces Indian Poker cards have been spread through the Internet, forcing the authorities into a game of whack-a-mole with possible producers of the cards.

Meanwhile, Misaki makes a separate investigation of the Indian Poker cards, but with the intention of taking care of the person responsible for its spread. She employs the assistance of Keitz Nokleben for the case, and the search of information brings them to links with Clone Dolly and the identity of the creator of the Indian Poker cards, Kuriba Ryouko. Keitz, however, struggles to find out more as Ryouko is part of a certain institution, and he begins wondering if the Kuriba Ryouko inside the facility is the person itself.

Misaki meets with Mikoto, who was still reeling from her failure to secure the Bust Upper card, and explains to the Electromaster her findings. According to the information she acquired, Kuriba Ryouko was a subject of a cyborg experiment where her body was split into two and was rearranged into two bodies, with machines replacing the missing body parts. The two "Ryoukos" were then separated and observed while living normal lives and the original Ryouko was pieced back together one year later with no adverse effects to her body and mind. Also, Ryouko retained the memories of the time she was split into two.

Mikoto sees nothing wrong with an experiment that might be used to aid persons with disabilities, but Misaki clarifies that the experiment also has another aim aside from testing the compatibility of cyborg technology, and it is the creation of a soul. Mikoto believes that the discussion of the soul is an occult topic. Regardless, Misaki asks Mikoto about what happened to Ryouko's soul during the entire experiment: "What happened to Kuriba (Ryouko)'s soul while she was split in two? If one Kuriba lost her life during that time, it's hard to believe the other one would die at the same time while somewhere else, right?" Misaki speculates that Ryouko's soul was also affected by the split in some way, and had two souls during the experiment. But, she wonders about what happened to the other soul after Ryouko is reassembled once again.

Although Misaki and her newest accomplice Kouzaku Mitori know that Mikoto has a tendency to immediately act on her own accord whenever innocents are in danger, the Rank 5 Level 5 decides to use the Sisters to hasten her cooperation. True enough, that night, Mikoto tracks down the high-rise building where the laboratory related to Ryouko's experiment is located. But, before even managing to infiltrate the building, an explosion rips through the lab, and Mikoto sees a girl in a lab coat who disappears after plummeting several stories into the ground. This girl would later sneak into Shinasame University DNA Map Analysis Laboratory, killing the thugs using the dilapidated complex as a makeshift base and scavenging items that she would need, including a hospital gown and enough artificial skin to cover her mechanical parts.

With the help of Keitz's findings, Mikoto and Misaki track down the original Kuriba Ryouko in an apartment complex and in a conversation, Ryouko echoes Misaki's fears about the existence of her artificial likeness, a Doppelganger, being used for dangerous things. In a worst case scenario, if the Doppelganger does have a soul, this soul could escape from the mechanical body it serves as a vessel, and could cause a widespread "possession" that will affect the entire Academy City. To avoid this, Kuriba created safety mechanisms for her Doppelganger and developed the Dream Ranker card system so that someone can use her knowledge to establish a breakthrough that is impossible for her to accomplish alone.

Shortly after the conversation, the original Ryouko returns to her apartment unit, only to discover that her Doppelganger has managed to track down her location and is about to get rid of her. In turn, members of Scavenger clash with their target, the Doppelganger, and a fight breaks out. To the shock of Scavenger, the Doppelganger quickly adapted to their attacks, and used her mechanical body to her advantage. Meanwhile, Seike, one of the members of Scavenger, tracks down the original to confirm that they found the right target, but Mikoto finds the original as she tracked her down again to apologize for her intrusion earlier. Mikoto confronts Seike despite the latter's intention of letting the original free, while the rest of Scavenger struggle against the Doppelganger who began to use their esper abilities against them. Seike was quickly defeated by Mikoto's electricity, and the rest of Scavenger manages to escape, only to stumble upon Mikoto. Through some careful deception, they manage to bring Mikoto to their aid.

After a short call from Misaki, Mikoto and the so-called Leader of Scavenger head to the next target of the Doppelganger, an airship that serves as a data center. With even Mikoto struggling to contain the Doppelganger, she and Leader continue trailing its path to a nearby radar facility, which is coincidentally near to Scavenger's drop-off point for the Doppelganger. Meanwhile, the rest of Scavenger reunite with Leader and take the chance to complete the mission of bringing the Doppelganger in working condition before escaping.

Mikoto begins her battle against the Doppelganger, who gains in size due to the rubble it has absorbed. Using her ability and experience, Mikoto manages to learn how to counter the Doppelganger's attacks. However, it quickly gathers large amounts of debris to create a colossal "shell" and began unleashing larger attacks on Mikoto. Mikoto responds by creating a massive construct made out of iron sand, an "iron sand puppet", to match the size of the Doppelganger. Using her Electromaster ability, Mikoto gains an upper hand over the Doppelganger's giant of concrete, but it begins to use the widespread "soul possession" to its advantage, forcing Mikoto to use up her powers to destroy threats to the surrounding area. Eventually, Mikoto's spread of iron sand in the air allows the Doppelganger to track down the location of her actual target, the data storage airship.

As the original Ryouko heads to her Doppelganger's location after uploading all the necessary data to save her ailing mother, the Doppelganger splits apart its massive construct into many of her copies, providing a distraction for Mikoto while the Doppelganger takes the original. Atop the airship, Ryouko proposes to her Doppelganger to wait for two months until her Dream Ranker cards has helped develop a way to erase a soul—in this case the original Ryouko's soul—so that the Doppelganger can obtain a new vessel. The Doppelganger refuses to be swayed by the original's proposal and decides to destroy her creator along with Academy City. Shortly, Ryouko is thrown off the airship by the strong winds, but was later rescued by Scavenger.

With a combination of Misaki's own information gathering and Leader's findings, Mikoto discovered that the Doppelganger is creating a kind of self-replicating artificial muscle that controls materials by embedding on them at the microscopic level, something that it developed ever since its conception. Mikoto uses these findings to conclude that the Doppelganger has no soul, and is acting out of despair after learning the truth. The Doppelganger once more enters battle against Mikoto, but she easily dispatches the Doppelganger's diversions with the help of Leader's ability. Eventually, Mikoto sees something unusual in the Doppelganger's actions, and it confirms this by stating its suffering and its intention of wanting to be destroyed.

By the Doppelganger's request, Mikoto destroys the data storage airship, and much of the Doppelganger's body was destroyed in the crash. The Rank 3 Level 5 finally understands the Doppelganger's plan of destroying herself, the airship that contained the data necessary to reassemble itself, and its original creator, Kuriba Ryouko. The original arrives with one of the lead researchers of the experiment by car, and the latter is devastated by the loss of assets during the latest incident, which is worsened by the original's plan to pull out of the experiment. In a fit of hysteria, the lead researcher pulls a gun and threatens to shoot Ryouko unless the Doppelganger is handed over, and it comes to a point where Mikoto's clarification of the nature of the Doppelganger's soul fails to reach the lead researcher. Ryouko tries to stop the lead researcher from using the Doppelganger in further experimentation, but Ryouko is shot in the torso, causing the lead researcher to run away in panic.

Mikoto tries to prevent Ryouko from bleeding out of her wound as Scavenger heads to their location (in the anime, this was changed to Kuroko heading to the location through Mikoto's call while Scavenger only called the hospital). Meanwhile, in its "dying" moments, the Doppelganger comments on its original's luck, as Ryouko's injury is located where much of the Doppelganger's internal organs are still intact. The lead researcher is shortly caught by Misaki, who resets his mind so that he is forced to retrace his steps in his medical science research on cyborgs.

Aftermath
With the help of the remaining functional organs from the Doppelganger, Ryouko manages to survive the gunshot wound and eventually made a steady recovery in a certain hospital. However, despite its apparent "death", the Doppelganger continues to manifest in Ryouko's mind, taking note of the girl's efforts in using the Indian Poker cards to save her mother. Acknowledging this, the Doppelganger starts looking over Ryouko's own research on creating a cyborg for her mother's recovery. Ryouko would later retell this unusual experience to Mikoto in a hospital visit.

Meanwhile, after Scavenger's completion of the mission involving the retrieval of the Doppelganger, the B-rank group discovers that their client organization has run out of money, forcing them to consider the possibility of not receiving any monetary reward for their actions. After Leader's negotiation with Scavenger's own liaison, despite the lack of rewards, the group instead regains their A-rank status. For the meantime, however, they are ordered to return to sleep until a new mission is made available.

Uiharu, who was injured after a violent encounter (see Battle Royale Arc), reunites with Saten on a quick tour around some of Academy City's known urban legend sites. After Saten comes into terms with the sudden disappearance of her newest friend Frenda Seivelun, she and Uiharu find themselves trying to cheer up Mikoto, who is in a daze after an encounter with a certain boy and discovering her own feelings towards him.

Trivia

 * This story arc, officially considered as the fourth arc and first fully-original arc of the Railgun manga series, is also the story arc that intersects with the most story arcs in the franchise at five.
 * At the time of its completion, the arc was also the first story arc to go past the chronological timeline covered by the Toaru Majutsu no Index anime series. As of the end of the Dream Ranker Arc, the timeline has reached past mid-October, about two weeks ahead of the last animated Index story arc chronologically at the time, the Skill-Out Uprising story arc.
 * This arc's story development is revealed via Railgun manga editor Ogino Kentarou, such as:
 * The idea of having Yumiya Rakko as a mid-boss in this arc is Fuyukawa Motoi's idea and it was not part of Kamachi's original plot for the arc.
 * Before deciding on the previous sniper of SCHOOL, Stephanie Gorgeouspalace was supposed to appear in this arc battling Frenda.