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.

Etymology
The name Shirai Kuroko is quite interesting because it contains both the meanings of "white" and "black".

The family name "Shirai“ (kanji: 白井) can be literally interpreted as "white" plus "(water) well"; while the given name "Kuroko" (kanji: 黒子) is more interesting: as a name, it can be interpreted as the stem "Kuro-" (meaning "black") plus the suffix "-ko" - which is commonly seen in Japanese female names (other examples include Saten Ruiko and Kongou Mitsuko); while not used as a name, the term "" means stagehands in traditional Japanese theater, who dress all in black.

These literal meanings of Kuroko's name have been referenced several times in the franchise:


 * In Toaru Kagaku no Railgun Episode 02, when Misaka Mikoto gets angered at Kuroko about the "computer parts", she says, "I'm going to char you as black as your name." 


 * In one clip in Toaru Majutsu no Index-tan Episode 02, a shadowy figure, who dresses all in black, carries Index-tan into the scene. This figure is an apparent reference to "kuroko" (the stagehands). Also, the two tawny ponytails extruding from the two sides of the top of this "kuroko" reminds us of Shirai Kuroko - another apparent pun on her name.


 * Kuroko's character song is titled Desu no! White & Black.

Appearance
Kuroko is a girl with tawny 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. Her hair is naturally curly and as such needs to get a straight perm for it.

With 152 cm she isn't very big and with a flat chest her appearance is the usual appearance of an average girl at her age.

As per ruling of both Academy City and Judgment, she wears the uniform of Tokiwadai Middle School and the Judgment armband though the latter only during on duty. 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 ignorant to the customs that present-day Japan still practices, 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. Another distinguishing characteristic of Kuroko is her feelings of romantic love towards Mikoto. In the ongoing Railgun manga her affections appear to be genuine and that she is truly in love with Mikoto. She even allows herself to get severely hurt in order to do what she can to help Mikoto. She is regarded as Mikoto's best friend.

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 and Touma 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.

Kuroko can be close-minded at times refusing to believe in urban legends without any concrete evidence and even then it will still take some time for Kuroko to accept it. Examples include the boy with the power to make other powers stop working, despite knowing him personally and it was not until when she saw the effects of the Level Upper that she began to suspect it and even than it was only after seeing it a considerable amount of times. Kuroko doesn't seem to like the idea of Gemstones, believing that such a phenomenon couldn't be possible without the Power Curriculum Program.

In her Japanese conversations, Kuroko has the habit of ending the determinative sentences with the auxiliary word "ですの" (desu-no), instead of "です" (desu) in standard Japanese language. This can be seen as her unique label in Toaru franchise. For example, Kuroko's catchphrase: " ジャッジメントですの！" (pronunciation: Jajjimento desu-no! meaning: I am Judgement! or This is Judgement!). This is also shown in her character song Desu no! White & Black.

Background
Not much is known about her past before entering Tokiwadai Middle School, but her family ran a major chain of convenience stores.

A year before she entered the prestigious Tokiwadai Middle School, Kuroko joined Judgment, 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.

In the April of the current year of timeline, Kuroko enrolls into Tokiwadai Middle School. She later falls in love with Misaka Mikoto, calling her "Onee-sama" (big sister), and then forces her way into her dorm, evicting Mikoto's roommate. The both of them later get punished for this act, but Kuroko stays as her roommate regardless.

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 Magnus and Kanzaki Kaori in the Anime. This is not in the Light Novels.

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
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
Kuroko faces off against Musujime Awaki 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. 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 ends up being pinned under a pile of furniture. Despite this, she continues to verbally assault Awaki, whose composure and teleporting abilities begin to break down as her psychological state of mind is rattled by Kuroko's taunts and rebuttals. Kuroko eventually manages to summon enough strength to overcome the furniture pinning her down and stand up to face her now-panicking opponent. Using a lamp as an improvised weapon, Kuroko charges at Awaki; the latter reacts by pulling out a gun and shooting her in the torso. Awaki, who is by then in the grip of a mental breakdown, decides to crush Kuroko by collapsing the upper floors of the building onto her. Kuroko, who is almost completely incapacitated and barely conscious, only just manages to be saved by Mikoto (who used her railgun to tear open an entry point into the building) and Touma (who grabbed Kuroko and then used 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 Kuroko. 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
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 Kazari. 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
Kuroko is next seen doing office jobs with 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.

Document of Constantine Arc
Members of Judgment including Shirai Kuroko and Uiharu Kazari were tasked in helping security during the Interceptor Show.

While Mikoto was searching for Kamijou Touma's home, she spotted Kuroko and Uiharu walking along the street and talking each other.

World War III Arc
In the novels, on October 31st, Kuroko was busy with Judgment work and wasn't present when Mikoto was thinking about World War III and Touma at the dormitory and when she saw Touma on a news report in Russia.

In the anime, Kuroko was present in the dormitory with Mikoto and watched a video of Academy City's declaration after intercepting the missiles fired by Russia. Later, while watching a news report on her laptop about World War III showing Russia, she discovered Touma in the bottom corner of the screen and informed Mikoto about it.

Ichihanaran Festival Arc
Although mentioned several times before, Kuroko reappears again in the novels at last and debuts silently in Shinyaku Toaru Majutsu no Index. She appears with Konori Mii across the road where Uiharu Kazari is. As a member of Judgment, it is her duty to aid Anti-Skill during the Ichihanaransai. She witnesses Mii calling out to Aogami Pierce for questioning, deeming him to be a suspicious person. Kuroko asks her on why they couldn't just throw him into a cell, as there are cases and mysterious reports that are needlessly driving down their efficiency, especially about rampaging Rhinoceros beetles. Mii says not to take her frustration on Aogami, to which she then asks for his belongings to check them.

That was the 43rd time he has been questioned by authorities that year.

Magic God Othinus Arc
In the second recreation of the world by Othinus, known as the Version_Beta world in-text, where another "Kamijou Touma" exists living Touma's life. In this world eerily similar to Touma's world, Kuroko is only referenced by Mikoto to be busy when she is forced to confront the sender of the junk mail to Tokiwadai's dormitory, a task that is usually handled by Kuroko according to her.

In the final recreation of the world by Othinus created specifically to break Touma's spirit, known as the Version_Omega world in-text, where several characters from the original world have been "saved" or have not experienced great tragedy, Kuroko, Uiharu, and Saten are in the festival where Touma is after his spirit has already been broken, trying to decide how he should have himself killed. Here, they are all aware of the existence of clones. Kuroko complains on how there are too many people in the festival and wonders where Mikoto had ran off to. Uiharu comments on how it would be impossible to find her in the festival with all the people who look like her. Saten then comments on how she just remembered that Meigo Arisa may be coming in secret, referring to her "perfect mode" after becoming one with Shutaura Sequenzia. Uiharu comments on how she saw the doll-like child president wandering around earlier, as such Arisa may be around.

Magic God Invasion Arc
Kuroko and Uiharu are in the same subway train as Akikawa Mie during her adventures in trying to get the liquid diamond to her mother during the shadow of the High Priest's rampage in Academy City. They were in a tunnel when the train suddenly stopped due to the damage done by the High Priest in School District 5's. After being told to leave through the emergency exit, Kuroko and Uiharu do their jobs and guide the passengers. Kuroko notices Mie run out of the train but since it was dark she could not do anything about it. She then asks Uiharu if the power is still not back up.

Touma makes use of Misaka Mikoto's connections with Judgment and her influence to prevent disaster from befalling when the High Priest used the dirt under the city for his magic. Kuroko and Uiharu are part of this bold plan, and as such they are near the headquarters where Mie's mother worked, directing people to safety as members of Judgment. Uiharu later asks Uiharu to arrange the routes so that there won't be any bottlenecks at bridges and intersections.

It is later revealed that all the actions of the people in the city where under the manipulations of Kihara Noukan, making calculations and sending out bait like the liquid diamond that Mie took to prevent human casualties during the High Priest's rampage.

Element Arc
On December 8th, Kuroko appeared with other Tokiwadai students when Mikoto brought Touma to School Garden, to her shock and dismay. After some manipulation from Misaki, Kuroko teleported Mikoto away to "tend" to her. She later saved Touma from the rest of the Tokiwadai girls, but soon after fainted from heatstroke and lack of sleep. She recovered but had to stay behind while Touma, Mikoto, and other students went to destroy the Crystal Tower, much to her chagrin. She and the defenders were later overcome by an Element led by Kihara Yuiitsu.

Aleister Crowley Arc
On December 11th, as Tokiwadai was being rebuilt, Kuroko was apparently going around looking after other students.

Coronzon Arc
Prior to going to Bali, Kuroko and the other girls are in Tokyo by a convenience store, waiting for Misaki and Mikoto to decide which country there were to go to after Academy City was shut down.

Kamijou Arc
Following Academy City's recovery, Kuroko and the other Tokiwadai students reunited with Misaka Mikoto and Shokuhou Misaki at the airport in School District 23.

Christmas Eve Arc
On the morning of December 24th, shortly after midnight, Shirai Kuroko was participating in the school's litter picking walk while thinking aloud what to do with Mikoto while they were confined to the dormitory at Christmas. These hopes were quickly dashed as Shokuhou used Mental Out on her to create a distraction as part of the two Level 5s' attempt to escape from Tokiwadai's strict Christmas oversight. Later in the morning, she was part of the group of Tokiwadai students and staff who were pursuing the escaped Mikoto.

Los Angeles Arc
Early in the morning on December 26th, under Shokuhou's manipulation, Kuroko attempted to leap into Mikoto's bed, only to find a pillow in her place. She was then swiftly knocked out by Mikoto, who went off to confront Shokuhou and found she had used the distraction to sneak off towards Touma's room. Later in the day, she returned from a counselling session to find the two Level 5s in a scuffle over the television and in an awkward position. Not long afterwards, when Touma phoned Mikoto for help in unlocking Melzabeth Grocery's phone for information, Kuroko interrupted the conversation and on recognizing and mentioning Melzabeth's name, ended up providing the information Touma needed.

New Year's Arc
On January 1st, Kuroko made a New Year's shrine visit in School District 12 together with Mikoto, visiting the same shrine that Kamijou Touma's group visited. During the visit, they encountered Shokuhou and Hokaze, as well as multiple Sisters. After being seeing and being concerned by the effects of the Kotatsu Syndrome amongst the student visitors, they were present when Alice Anotherbible, accompanied by Trismegistus and Good Old Mary, greeted Touma.

The Fourth Friday of April
Kuroko enters Sakashima Michibata's salon and tells him to put down his handheld game or else she'll give him some trauma. Kuroko is concerned because Michibata seems unconcerned of getting customers for the salon. Even the staff members that have been only employed there for three months are more worried than Michibata. Regardless, Kuroko goes to a partition and sits down on a chair to get her hair down. Michibata who is unintimidated goes to her and removes her hair ribbons to begin his work. Michibata suggests to Kuroko in using new irons he just acquired and asks if she wants a drill or croissant, saying she can be a very domineering. Kuroko doesn't want to, saying that her hair is naturally curly and as such she wants him to give her a straight perm. Michibata asks if it is an she wants, to which Kuroko reiterates, by yelling at him, that she wants a straight perm as he puts on the hair dryer helmet on her head.

Afterward as Michibata pulls out a thin pair of scissors, he tells Kuroko that she must have it tough as she is in a prestigious esper school like Tokiwadai and that she needs to get a teacher's permission for the salon she chooses to get her hair cut. He tells that though their school chose him as a designated shop and allowing him to get a lot of easy money, he says that it must be pretty constrained for her having those rules. Kuroko retorts that complaining won't do a thing, saying that it is because people like him can get a basic genetic sample from hair and blood, and as such the school doesn't want someone secretly collecting and mapping someone's DNA. As he continues with Kuroko's hair, he looks above his head the large number of cameras installed by Tokiwadai Middle School. Michibata then says that he has heard a rumor that there is a new subsidy for research on developing teleportation powers as dealing with 11th dimensional coordinates is difficult enough that it is unpopular with the scientists. Kuroko tells him it is not because scientist dislike 11th dimensional calculations, as they most often come up in the quantum theories related to Schrödinger, and says that the higher ups are just worried that there aren't many espers that can teleport. Kuroko says that there are just abilities that show up easily and some that don't. Michibata notes that is one of the mysteries regarding esper powers as he is sure students go through the same Power Curriculum Program but end up with different powers. As he continues to cut Kuroko's hair he wonders why Academy City is even developing powers in the first place, to which she says that he should not deny the very root of Academy City's reason to exist.

Michibata responds that he understands that esper powers are an attractive prospect but says that he thinks that there's some influential person behind it all who dreams of eternal life or world domination. He says to her that he wonders if the text book on esper powers for students like Kuroko even talk about the uproar during the Cold War, referencing the United States and the Soviet Union investing money in it. Kuroko then references the Stargate Project. Kuroko says that they have learned about the project in history class, saying that the scientist had no idea what they were doing and repeatedly kept doing their large-scale experiments despite their inconclusive findings. She concludes that the scientists were just fumbling around and wasting federal funding. Michibata wonders if the project was truly for developing esper powers for military use. He thinks that the project was more for selfish reasons such as being special than for military use. As he continues cutting hair, he then asks if the esper power development between the US and the USSR during the Cold War get their "esper samples". Kuroko says that maybe they were bluffing. Michibata responds that he doubts all of them are fakes, and says that at the very least he doesn't think anyone would wish to create something like an esper without seeing one. Kuroko uses Alchemy as an example, saying that royalty and nobility believed in alchemy because they thought that they had witnessed it with their own eyes, essentially implying that people don't need facts or evidence to believe in something.

Michibata then says that he doesn't believe in superstitious stuff like Alchemy, UFOs, or the New Jersey Devil. Hearing this, Kuroko asks if Michibata is implying that some information on Academy City technology got leaked to the US and the USSR during the Cold War, to which Michibata says that it would be impossible due to the high difference in technology between the outside and Academy City as it would not help them because they did not have the technology to break the advanced encryption. He continues by saying that an "outside" supercomputer in the past wouldn't have been powerful enough to run even the handheld game he is playing, much less crack the encryption and read any information they attained from Academy City. Kuroko then asks what he is implying, to which Michbata asks if she has heard of Gemstones. Kuroko is silent for a moment, and Michibata then asks if he has upset her. Kuroko says that he did, saying that her power was brought up by the stimulation of her brain through the Power Curriculum Program, and says that she would rather have him not bring up the term Gemstones. Michibata simply calls it a simple difference between an artificial diamond and a natural one. He says that if a certain phenomenon has been caused artificially, then as long as the same circumstances as in the experiment are recreated in the natural world due to some factor or another, the same phenomenon will occur with no help from humans—basically saying that if espers due to Academy City's curriculum can exist then so do espers in the outside through natural means that are similar to the curriculum. He then compares them as espers being a stun gun and Gemstones being a bolt of lightning. A bored Kuroko denies their existence, saying that Gemstones are just a hypothesis, stating that it is because she has never seen anything like a Gemstone and even if they did then the sample size would be extremely small, a mere error in the data and wouldn't even show up in the total results.

Hearing this, Michibata just smiles and once again challenges her in this debate by using her stun gun and lightning, asking if she thinks lightning strikes rather frequently, to which she says that they do, though extremely rare for it to strike a specific person.

The Third Friday of September
After Uiharu Kazari uses a virtually impossible to crack encryption, the Omega Secret, on the Bank, its server controls, and maintenance tools, in order to prevent a high-level Electromaster intruder from accessing data instead of cutting access to the Bank, Shirai Kuroko goes back to Judgment 177 Branch Office. Here, she tells the bewildered Uiharu that she has gone too far and decides to lecture her.

Shinyaku Toaru Majutsu no Index SS
Mikoto and Kuroko are in the shopping district that Index also goes to, leading to a bunch of misunderstandings thanks in part due to Touma’s advice to Index, with Index assuming Mikoto wants Touma’s money and Kuroko becoming suspicious with Mikoto for being violent in back alleys. In the end, a truck passes by before the girls creating a draft, leading to Mikoto and Kuroko’s skirts to be blow upwards.

Seeing this, and the fact that Index has seen a handiwork of a magician in play, Index offers the money to them, to “pay-off” trouble, as Touma advised, much to Mikoto’s chagrin. They of course later decline her offer.

Toaru Majutsu no Index Movie: Miracle of Endymion
Kuroko, still in a wheelchair from her fight with Awaki, first appears in a family restaurant, and makes a scene there, only to be shocked by Mikoto.

She later reappears with the rest of the gang, accompanying Meigo Arisa as she goes to a photoshoot. She rants about Ladylee Tangleroad not being the real CEO of Orbit Portal Company, and comments on her queer existence. She later, much to her shock, meets Ladylee herself, initially thinking of her as a doll, as she greets Arisa. Kuroko is with her camera as the bombing of the mall they were in begins, and teleports Saten and Uiharu quickly away. She later returns to the scene of the accident, asking if anyone is hurt, but then discovers that a miracle has happened, and everyone is unscathed.

She later teleports Mikoto towards one of the bridges that leads to Endymion during the climax of the movie, allowing her to destroy a large mobile weapon that prevented Anti-Skill from entering the Endymion, as they have discovered it has been sealed. Mikoto tells Kuroko to stay put as she is still injured. Kuroko is forced to acquiesce as her injuries act up again. She later teleports to Anti-Skill's command post as Uiharu discovers that Endymion is about to collapse and they need to destroy the explosive bolts to break it away. Kuroko offers to help Mikoto, but her injury prevents her from doing so. Tsuchimikado Motoharu later contacts them to be a volunteer in destroying one of them, though later has Stiyl Magnus do it instead.

Later, when Anti-Skill is too overwhelmed by Endymion's defenses to even get near one of the explosive bolts, Misaka 10032 contacts them, stating that they will aid it. Kuroko becomes confused as she refers to herself as Misaka, though no more comment is made of this.

Toaru Majutsu no Virtual-On (game)
Kuroko is one of the playable characters in the Toaru Majutsu no Virtual-On video game. Her associated Virtuaroid is RVR-14/VSL Fei-Yen kn.

Ookami-san and her Seven Companions
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.

Dengeki Bunko Fighting Climax
Kuroko is one of the new characters added to the game in the Ignition update. She fights by using her martial art skills, teleportation and steel darts. One of her Climax Arts consist of her using a large belt of darts (like the one she used in her fight with MAR in the climax of the Poltergeist Arc) on the opponent, finishing the attack with a teleporting drop kick. In the other she teleports herself and the opponent inside a building, just before using glass panels to cut the support pillars and destroy the building like she did in her fight with Trick, only this time she leaves her opponent behind when she teleports away. Her Trump Card consist in teleporting and hitting the enemy with a wheelchair, based on her doing the same during her first encounter with Kouzaku Mitori.

Dengeki Bunko Crossing Void
Like Fighting Climax, in a gacha-RPG game, she returns as one of the playable characters (Main and Support, with a Maid variant)

References in other media

 * In Episode 6 of the second season of the anime Haiyore! Nyaruko-san W, Cthugian Kuuko plans to have a baby with the male main character Mahiro. Trying to combine their both names, Kuuko proposes to name the baby "Kuroko". After that, she says "If it is a boy, he will play basketball. If it's a girl, we'll enroll her in Academy City."
 * Near the end of a news video about a controversial Taiwanese High School Christmas Parade in 2016, Kuroko was shown repeatedly banging her head against a desk in disbelief.

Teleport
Her ability is Teleport (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.

Not only is she able to teleport objects inside designated targets, allowing her to "throw" the darts she carries on her thighs with perfect accuracy, but she can also change their resulting orientation, shown when she teleported a standing Uiharu above a standing Mikoto such that their heads would collide. 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 spatial 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. According to Kouzaku Mitori there is a one second lag when consecutively using her power in fights leaving her vulnerable in that one second interval before teleporting again. The one second teleportation lag is not referenced in the anime, due to Kuroko's teleportations only have delays up to a minimum of 0.4 seconds, obviously seen where she teleports Keitz and Misaka 10032 and then teleports quickly again when she gets attacked by Mitori's shadow puppet, with a delay of approx. 0.4 seconds.

Other abilities
Aside from her esper ability, Kuroko mainly relies on the skills she learned from training, which emphasizes throws and take-downs that compensate for her small size. Kuroko specifically focuses on drop kicks. Although usually displayed and used as comedy relief, Kuroko even displays a strong constitution, surviving constantly shocks from Mikoto, having her neck dislocated by the Dorm Supervisor, repeatedly pounding her head on solid objects in fits of either rage or terror or stupidity.

Kuroko can use a handgun, as part of her Judgment training. However, she has difficulty with other kinds of guns, and may waste a shot on something harmless if it catches her by surprise.

Equipment
In addition to her darts, Kuroko carries small ball-shaped handheld devices made to interfere with listening devices for security purposes. She uses these to deafen the echolocation of Mitori's Liquid Shadow puppet. During the October 4th Park Fire, Kuroko wears a monocle and mouthpiece-type gas mask.

Misaka Mikoto
She has been apparently in love with Misaka Mikoto for a long time, whom she calls "Onee-sama" (meaning big sister - in the English dub Kuroko refers to her as "Sissy"); when she has the chance she keeps a 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. These attempts have toned down in the manga. Despite her overzealous attempts at gaining Mikoto's favor, her affections appear to be genuine; it has been shown on a few occasions that she is genuinely in love with Mikoto, even allowing herself to get severely injured and hurt in order to help Mikoto. She is regarded as Mikoto's best friend.

Kamijou Touma
Kuroko's relationship with Touma is mostly rivalry and jealousy over his encounters with Mikoto even though Touma himself is not aware of this. Despite this, she has also acknowledged him as someone able to stand at the same stage as Mikoto and truly support her when she herself can't.

Uiharu Kazari
Uiharu and Kuroko met when they were having their Judgment training. They are seen working together and hanging out with their friends, and are seen being good friends throughout the series except for when they got in an argument about rushing into danger without thinking.

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 art style 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 an in-joke for the anime producers, considering Kuroko can also mean "black child" literally in kanji and also because the episode was aired during the US presidential elections.
 * Satomi Arai's comedic yet thoughtfully mature performance as Kuroko won her the Best Supporting Actress trophy during the Annual Voice Actor Awards in 2010.
 * 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 spikes are labeled with "Kuroko".
 * When Kuroko's memories of Misaka Mikoto are erased during the Daihaseisai, Kuroko reacts to Mikoto's close contact, exclaiming, "I'm straight, I swear~!!" This implies that she believed she was straight before she met Mikoto and became infatuated with her.

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