A Certain Magical Index/Characters/A Certain Scientific Railgun Sub-Series Protagonists

The heroines of To Aru Kagaku no Railgun, the spinoff Prequel and side story of To Aru Majutsu no Index, which places its protagonists focus on Mikoto Misaka.

They are a quartet of junior-highschool girls, whom through the law enforcement ties of Kuroko and Kazari, (not to mention the enthusiasm of Ruiko), become involved in the myriad of Urban Legend that permeate Academy City. Soon becoming fast friends, they form a "detective club" of sorts that sets out to solve the mysteries of this sprawling metropolis.

Our quartet of heroines share the following common tropes when they are together:
 * Four-Girl Ensemble
 * Mikoto is the Mannish-One
 * Kuroko is the Sexy-One
 * Ruiko is the Wild-Card
 * Kazari is the Girly-One
 * Four-Temperament Ensemble:
 * Mikoto is Choleric
 * Kuroko is Melancholic
 * Ruiko is Sanguine
 * Kazari is Supine
 * Kid Detective: The quartet's favourite pastime together is ametuer detective-work focusing on Urban Legends in particular.
 * Sweet Tooth: Often seen discussing the clues to the latest mystery over a mouth-wateringly delivious looking chocolate parfait.
 * True Companions

Mikoto Misaka
"See To Aru Majutsu no Index"

Kuroko Shirai
http://static.tvtropes.org/pmwiki/pub/images/300px-Kuroko Shirai_391.jpg

"Voiced by: Satomi Arai"

One of the main characters of A Certain Scientific Railgun, she is Mikoto's junior in Tokiwadai Middle School, a Level 4 Esper, and a member of Judgment. She has an obsessive crush on Mikoto, who she calls "Onee-Sama", and is on the constant lookout for a chance to... get close to her (which Mikoto rarely allows and even more rarely appreciates). - "Kuroko: "Oh, the whip of Onee-sama's love!""
 * Abhorrent Admirer: Zig-Zagged depending on her clingyness.
 * Alpha Bitch: Her attitude at times.
 * Amusing Injuries / Slapstick Knows No Gender: It seems Saeba Ryo's problem also applies to female perverts.
 * Authority Equals Asskicking
 * Awesomeness By Analysis: To teleport, she has to make calculations on factors like mass, volume, vector, etc.
 * Back-to-Back Badasses: With Mikoto and
 * Badass Adorable
 * Barely-There Swimwear: Her outfit in Episode 13 is unforgettable.
 * Bunny Ears Lawyer: Yes, she is completely obsessed with Mikoto. But she's also an experienced member of Judgment who is skilled in the detective/law enforcement required for her job.
 * Catch Phrase: "I'm/We're from Judgement!" and "Onee-Sama!"
 * Clingy Jealous Girl
 * Cry Cute: Towards Mikoto's rejections.
 * A Day in The Limelight: (Index) Volume 8 of the novels, or the Remnant arc in the anime (Episodes 6 and 7 of Season 2).
 * Electric Torture: How Mikoto usually rewards her attempts to have sex with her, and always Played for Laughs.
 * Expressive Hair: Her pigtails.
 * Fille Fatale: A bit too sexually aggressive for a thirteen year old girl for comfort...
 * Forgets About Her Powers: Despite her often ingenious uses of her power, she sure gets punched in the face a lot for someone who can teleport instantly.
 * Justified in that teleportation powers rely on incredibly complex 11th dimension calculations, something that even a Level 4 like Kuroko has difficulty with when she's caught by surprise or dealing with unpredictable situations. Unfortunately, teleportation is not something one can do by instinct.
 * Girlish Pigtails
 * Hard Head: She would already be a vegetable were it not for this trope, considering how she normally deals with stress. See Use Your Head below.
 * Head Desk: See Use Your Head below.
 * Japanese Pronouns: Uses watakushi, the more formal form of watashi, as a first-person pronoun, which is linked to her being an Ojou.
 * Little Miss Badass
 * Locked Out of the Loop: Has no idea of the Sisters or of Mikoto and Touma's adventures.
 * Lovable Sex Maniac: There's something very funny about her attempts to get frisky with Mikoto.
 * And after seeing Mikoto's Hot Mom, she already got fixated on the latter's assets, complete with glaring red eyes, and probably would have taken a grab real fast if she hadn't been confined to a wheelchair.
 * Meaningful Name: Shirai Kuroko's name literally translates as "White-Well Black-Girl", a contrast that reflects her outwardly cute but inwardly perverted persona. Mikoto even points this out in Episode 2 before beating her senseless, shouting "I'm gonna fry you as black as your name!!" 
 * Moment Killer: Amazingly, in addition to the usual examples, Kuroko is this to herself. Many is the occasion where she has a touching, heartwarming moment with Mikoto, only to have her feelings get the better of her and abruptly launch herself at Mikoto getting beaten down as a result. She also has a habit of ruining tender Touma and Mikoto moments.
 * Murder the Hypotenuse: See Ungrateful Bitch below.
 * No Sense of Personal Space:
 * Ojou: Her highly refined and ladylike speech-pattern fits this trope perfectly. On the other hand, she possesses some decidedly unladylike tropes.
 * One Girl Army: Due to her very intelligent use of her already flexible power.
 * Power Perversion Potential: Which she uses to her full advantage.
 * Psycho Lesbian: A rare fundamentally good and heroic example of this trope.
 * Rape Is Love: "If you're more forceful, they'll have to pay attention", so she reasons.
 * Reasonable Authority Figure: Were it not for her perverted streak, Kuroko is the picture of a responsible, by-the-book, and honest "Good Cop" in the Judgment Brigade.
 * Schoolgirl Lesbians: Although it plays a minor part in Index, it's cranked Up to Eleven in Railgun.
 * Single-Target Sexuality: Even though she's a lesbian, the only girls she’s ever interested in are the Misakas. Yes, not only Mikoto but her mother as well! There's a reason why Mikoto keeps the existence of a closely guarded secret.
 * That aside she is also a deeply sentimental girl whose heart is easily warmed by the heterosexual romance of people she comes to care for or respect, like the Dorm-mother in Episode 18 of Railgun.
 * Star-Making Role: For Satomi Arai. It even landed her a "Best Supporting Actress" trophy for the 2010 Annual Voice Actor Awards.
 * Teleporters and Transporters: Her Esper power, "Teleport".
 * Tele Frag: By teleporting one object over another, she can displace matter occupying the old space. She once tore down a building by teleporting sheets of glass into the support pillars using this feature of her esper power.
 * Third Person Person: On occasions.
 * Tomboy and Girly Girl: With Mikoto; she's the girly girl.
 * Too Kinky to Torture: To be fair she had just (accidentally) taken an aphrodisiac, which was probably responsible for her reaction. It's still not really too out of character for her though.


 * Twin Tails
 * Ungrateful Bitch: Vows to murder Touma for (unwittingly) earning Mikoto's love in spite of the fact he saved her from a painful certain death at the hands of a superior teleporter.
 * YMMV, as going by later interactions she wasn't actually serious about said vow.
 * Also, some degree of Status Quo Is God may be in play.
 * Unknown Rival: Touma is oblivious to how much she wants to get him out of the way so she can have Mikoto all to herself.
 * Use Your Head: How she literally beats the frustration out of herself.
 * Verbal Tic: "Desu No"
 * Yandere: See Ungrateful Bitch above for more details. It's played entirely for laughs, though.

Ruiko Saten
http://static.tvtropes.org/pmwiki/pub/images/300px-Ruiko Saten_6320.jpg

"Voiced by: Kanae Ito"

Uiharu's friend and classmate, a Level 0 from Sakugawa Middle School, and another protagonist from A Certain Scientific Railgun. While she's not a member of Judgment, she does help them in any way she can. -
 * Adaptational Attractiveness: In the anime.
 * Ascended Extra: While she has a major role in the Level Upper arc of the comic series, she's eventually shifted out of focus once that arc ends. In the anime, she's one of the lead characters.
 * Audience Surrogate: The only unambiguously "normal" human in the entire franchise.
 * Batter Up: Often carries an aluminum baseball bat.
 * Cool Big Sis: To Uiharu.
 * The Everygirl
 * Genki Girl: She tries to be one.
 * Heroic Bystander: In episode 1 she saves a little boy from being kidnapped by a bank robber who has powers.
 * I Just Want to Be Special: The poor girl just wants an ability, even if its only Level 1.
 * Names the Same: Her surname is the same as a character in Needless, which led to some funny fanart.
 * Nice Girl
 * No Sense of Personal Space: Loves to flip Uiharu's skirt just to see her panties, especially if they're in public.
 * Odd Friendship: She seemed to have developed this with
 * Plucky Girl
 * Rapunzel Hair
 * Flower in Her Hair
 * Long Hair Is Feminine
 * Sailor Fuku: Her school uniform.
 * Star-Making Role: Kanae Ito's touching and sincere performance as an ordinary every-girl who nevertheless refuses to stop hoping and dreaming struck a chord with the audience as someone that anybody can relate to, and firmly established her place as a formidable character-actress in the anime landscape.
 * Stepford Smiler: In Academy City, life is hard for anyone who doesn't "measure up".
 * Too Dumb to Live: She was borderline during the the Railgun SS.
 * Sailor Fuku: Her school uniform.
 * Star-Making Role: Kanae Ito's touching and sincere performance as an ordinary every-girl who nevertheless refuses to stop hoping and dreaming struck a chord with the audience as someone that anybody can relate to, and firmly established her place as a formidable character-actress in the anime landscape.
 * Stepford Smiler: In Academy City, life is hard for anyone who doesn't "measure up".
 * Too Dumb to Live: She was borderline during the the Railgun SS.
 * Too Dumb to Live: She was borderline during the the Railgun SS.

Kazari Uiharu


"Voiced by: Aki Toyosaki"

One of the main characters from A Certain Scientific Railgun and a minor character from Index. She is Kuroko's friend and colleague in Judgment, a Level 1 Esper who goes to Sakugawa Middle school and is known for wearing a headband made of flowers on her head (and sometimes a surgical mask in the manga). Usually shy and humble, her personality can quickly change to overly excited, especially if it concerns the life of the upper-class (particularly anything involving Tokiwadai). -
 * Adorkable
 * Ascended Extra: Much like Saten, she's not really all that important outside of the first story arc in the original manga. In the anime, her importance is significantly boosted.
 * Badass Bookworm: She’s not a warrior in the least, but her computer expertise makes her just as (if not more) formidable as a dozen warriors in the right situations. She is in fact, so good at this that she can defeat even electrokinetic espers when it comes to hacking computers.
 * Cloudcuckoolander: She seems to edge into a state like this whenever she's in front of a computer.
 * The Cutie
 * Did You Just Flip Off Cthulhu?/ : In Volume 15 of the Index novels, Uiharu
 * Flowerbed In Her Hair
 * Fluffy Tamer: Everyone else took one giant step back upon meeting Kongo Mitsuko's snake, Ekaternina. Uiharu stayed behind to coo over it!
 * Get a Hold of Yourself, Man!: In episode 23 of Railgun she suffers a Heroic BSOD when  which results in some Inelegant Blubbering until Kuroko slaps her across the face and says "When are you going to stop crying?
 * Ill Girl: In the manga, where she suffers from constant bouts of the flu.
 * Kawaiiko
 * : Narrowly Averted in Volume 15 of the Index novels
 * Little Miss Snarker: Towards Kuroko.
 * Mission Control: Often plays this role, usually with Kuroko on the other end.
 * Nice Girl
 * Playful Hacker
 * Plucky Girl
 * Red Baron: Known as the "Gatekeeper" among hackers.
 * Sailor Fuku: Her school uniform.
 * What Kind of Lame Power Is Heart, Anyway?: As the only named Level 1 of the series so far, its no surprise her ability seems unimpressive.

For the supporting cast of this series, see To Aru Kagaku no Railgun Supporting Cast