Shirai Kuroko

Shirai Kuroko (白井 黒子) is a level 4 esper and a student of Tokiwadai Middle School, as well as a member of Judgment. She can usually be found accompanying the third-ranked Level 5 esper Misaka Mikoto — her best friend, partner, and roommate. Though a minor character in Toaru Majutsu no Index, she gets a starring role alongside Mikoto in the Toaru Kagaku no Railgun sidestory.

Appearance
Kuroko is a girl with auburn hair tied into two curly pigtails; the rest of her hair is left to hang as two rows of fringes divided in the middle. Her pigtails are tied in place by a red bow each.

As per ruling of both Academy City and Judgment, she wears the uniform of Tokiwadai Middle School and the Judgment armband.

On her thighs, she secures a pair of black straps where she stores the metal spikes used to secure criminals.

Personality
Kuroko can be described as a "girl living in the future". She is used to the world 30 years from now portrayed by Academy City and is thus ignorant to the customs that present-day Japan still practice, like the "love umbrella", which students usually use to link their names to the name of their crush, and the conventional technology outside Academy City.

Aside from being a girl with a modernistic outlook, she can also be blunt when giving her opinions, and this has caused her to be at odds with Uiharu once. She is equally blunt and honest when it comes to her sexuality, oblivious (or rather, uncaring) of the discomfort that her aggressive expression of lesbianism causes in others, especially Mikoto, the target of her lust. Whenever she and Misaka are together (despite being in public) she will run up to embrace Misaka and indulging herself on Misaka's body, despite knowing she will get shocked as a result of her actions. Her tendencies to get intimate with Misaka are often expressed to almost ridiculous lengths; for example, when the two are forced to clean a pool, Kuroko tries to trick Misaka into drinking an aphrodisiac, of which she ultimately fails and drinks it herself by accident.

Her desire can be aroused by anyone who even resembles Mikoto, even her beautiful young mother Misaka Misuzu. She even tried to steal some of Mikoto's underwear and even became aroused by the smell of Mikoto's bed. It is for this reason that Mikoto tried her best to keep the existence of her "sisters" a permanent secret from Kuroko.

Although usually laid-back and friendly, Kuroko portrays determination and confidence in her own abilities when she encounters enemies, even to those whom she knows is more powerful than herself. To her credit, she is an honorable girl who keeps her word, is kind to children, and shares with Mikoto the same ironclad sense of justice that makes neither of them ever back down in the face of adversity. According to a particular rumor concerning her and Mikoto: "There's this horrifying teleporter in Judgment who'll tear apart your body and soul if she catches you...and there's another that rules over even that teleporter's body and soul - the strongest Electromaster," although Kuroko had no knowledge of this rumor until a robber she took down told her about it in To Aru Kagaku no Railgun episode 1.

Kuroko doesn't seem to like the idea of Gemstones, believing that such a phenomenon couldn't be possible without the Power Curriculum Program.But she thought otherwise when she saw the effects of the Level Upper.

Background
Kuroko is a first grader from Tokiwadai Middle School. A year before she entered the prestigious school, Kuroko joined, a special public committee group whose duty is to maintain peace and order in Academy City. The first major case she handled (along with Uiharu Kazari and Konori Mii) was the arrest of a bank robber who can use the esper ability Equal Speed. Despite her young age, she stood up to the much older esper and was beaten up in the process, although a particular bolt of lightning saved her from imminent danger.

She is apparently in love with Misaka, whom she calls "Onee-sama" (big sister); she is on the constant lookout for a chance to get physically intimate with Misaka (getting called a pervert and electroshocked in the process), and tends to get jealous if someone else gets her attention; this unfortunately happens to Touma.

Level Upper Arc

 * Main article: Level Upper Arc

Kuroko is seen doing her duty as a member of Judgement detaining espers whose powers were enhanced by Level Upper. Due to injuries she sustained from fighting Level Upper users, she couldn't partake in rescuing Uiharu from Kiyama Harumi or help Mikoto fight the AIM Burst.

Big Spider Arc

 * Main article: Big Spider Arc

Kuroko aids Mikoto, Konori Mii, and Kurozuma Wataru in fighting and putting an end to the Skill-Out gang, Big Spider.

Poltergeist Arc
Kuroko is first seen in this arc with Mikoto and Ruiko helping Uiharu's new roomate move in. Later they go to a festival where a Poltergeist happens, and after observing Erii's odd behavior right before the incident and some investigation, she begins to suspect that Erii is the one responsible, which strains her relationship with Uiharu. When the head of MAR, Therestina Kihara Lifeline's true intention for Erii and Kiyama's students was discovered, she slapped Uiharu to snap her out of her emotional breakdown. Later, she and Mitsuko joined forces to stall the MAR powered suits, then came to Mikoto's aid against Therestina herself. At the lab, they are again confronted by Therestina, only this time she Capacity Down to disable them, except for Saten as she was a level zero and thus uneffected by capacity down, and went ahead to disable it, an act that earned her Kuroko's respect.
 * Main article: Poltergeist Arc

Index Arc

 * Main article: Index Arc

Her debut was in the 1st arc where she is on patrol investigating some strange incidents happening in the city due to Stiyl and Kaori in the Anime. This is not in the Light Novels.

Sisters Arc

 * Main article: Sisters Arc

She makes her first appearance to Touma in the 3rd volume where she's shocked to see Mikoto is with him, giving him a threat to not lay a finger on her. Later, when Touma decides to investigate the Level 6 Shift Project she meets him again at the dorm where she manages to hide him away from one of the dorm supervisors.

Kazakiri Hyouka Arc

 * Main article: Kazakiri Hyouka Arc

Kuroko is seen hunting down Sherry Cromwell, who had entered the city illegally, and tries to apprehend her but is stopped by her golem. She is saved by Mikoto who also happens to be on the scene. She later appears to help the people stuck in the underground part of the city, teleporting civilians out of the area as Anti-Skill is preparing to fight against Sherry.

Tree Diagram Remnant Arc

 * Main article: Tree Diagram Remnant Arc

Kuroko faces off against Awaki Musujime who has a remnant of the Tree-Diagram, but is out-classed as Awaki proves to be the better teleporter. Awaki teleports a corkscrew into Kuroko's side, as well as several spikes, and even shoots her with a gun. Kuroko returns the favor back at Awaki during their second encounter, but due to Kuroko being on the move all night without rest, she finds she cannot teleport anymore and so she resorts to psychological tactics against Awaki. Awaki's accuracy starts to fail, but then she decides to teleport a 4.5 ton object onto Kuroko. Kuroko, unable to do anything, is saved by Touma who uses his Imagine Breaker to stop the teleport. Kuroko is then taken to the hospital.

At the hospital, Touma visits to see how she is healing up, and accidentally walks in when Kuroko is changing clothes. He is rewarded with a slap from Mikoto (with electricity accompanying it). Later Kuroko jokes that Touma likes girls who are less aggressive, but after seeing Mikoto take the suggestion seriously, she gets upset thinking Mikoto really has fallen in love with Touma. Kuroko vows silently to herself to get stronger herself so that Mikoto will rely on her more, and not be a burden after the 'Tree Diagram Remnant' incident.

Daihasei Festival Arc

 * Main article: Daihasei Festival Arc

Kuroko is unable to participate in the Daihasei festival due to her injuries from the Remnants incident, and is in a wheelchair during the course of events, escorted by Uiharu. She is seen to cheer up for Mikoto who is taking part in a competition between schools. After seeing Mikoto taking care of Touma on a public TV screen, she vows to kill him for taking advantage of Mikoto and stealing her rightful place.

Academy City Invasion Arc

 * Main article:Academy City Invasion Arc

Kuroko is next seen doing office jobs with Kazari Uiharu and wonders about the strange situation in Academy City, although she is shown to be aware of the news of an intruder due to television announcements.

Abilities
Her ability is instant teleportation and she is called a Teleporter (空間移動 (テレポート)  能力者) because of this. Such an ability allows her to teleport herself and anything in her possession a certain distance in the blink of an eye. In volume 8 it is stated that her powers do have limits, being able to transport a total weight of 130.7 kilograms, to a distance of 81.5 meters from herself. It was revealed in Volume 3 of the Toaru Kagaku no Railgun Manga that before she went to Tokiwadai Middle School, she could teleport objects and other people, but not herself. She was eventually able to teleport herself sometime after enrolling in Tokiwadai. She is able to teleport objects inside designated targets, allowing her to "throw" the darts she carries on her thighs with perfect accuracy. One disadvantage of her power is that she has to concentrate on where she, the object(s), and/or person she holds will be teleported to, while working out the spacial co-ordinates of jumping between 3-dimensional and 11-dimensional space, so any disturbance in her concentration will render her powers useless, as demonstrated in her fight against Sherry Cromwell. Aside from her powers, Kuroko mainly relies on her Martial Arts abilities, which emphasizes throws and take-downs that compensate for her small size. ? Kuroko specifically focuses on drop kicks especially.

Other Appearances
Kuroko appears briefly in Ookami-san and her Seven Companions (also produced by JC Staff Animation Studios), smiling mischievously at the audience as a potential bride candidate for the boy millionaire Nezumi Chuutaro. This is, in combination with sharing the same animation studio, a result of Kuroko's voice actor rather blatantly using Kuroko's voice for the part of the series narrator.

Design evolution
There is little change in Kuroko's design. Haimura simply read her description and drew her without any real influence in her design. During her role as the primary heroine in volume 8, Kuroko's design was slightly modified to reflect her importance in the story; It is unclear what changes were exactly implemented.

By volume 12, Kuroko becomes affected by deformed artstyle that Haimura has for the characters. Kuroko was designed with white ribbons for her winter uniform, but this is not brought up in the anime adaptation. According to Haimura, Kuroko was the easiest character to transfer in manga format, for her detailed design for the Toaru Kagaku no Railgun manga.

Trivia

 * In episode 15 of the Index anime adaption, during the Angel Fall arc, Shirai Kuroko is depicted to have apparently switched with the US President Barack Obama, using his catchphrase "Yes. We. Can". This was not in the Light Novels, and could be seen as a in-joke for the anime producers, considering Kuroko can also mean 'black child' literally in kanji and also because the episode was aired during U.S.A. presidential elections.
 * Satomi Arai, whose comedic yet thoughtfully mature performance as Kuroko won her the Best Supporting Actress trophy during the Annual Voice Actor Awards in 2010.
 * Although usually displayed and used as comedy relief, Kuroko displays a strong constitution, surviving constantly shocks from Misaka, having her neck dislocated by the Dorm Mother, repeatedly pounding her head on solid objects in fits of rage/terror/stupidity and having her joints pierced by Musujime, from which she recovers quickly.
 * There are hints throughout the Toaru Kagaku no Railgun anime which suggest that Kuroko is fairly adept with a camera, and may possess some degree of skill in photography.
 * Kuroko also has a collection of Misaka Mikoto's pictures that she keeps in an album named "Onee-sama's secret" as shown in Toaru Kagaku no Railgun anime episode 2.
 * Her ability is listed as No. 478 in the Bank.