The first arc of A Certain Scientific Railgun, consisting of chapters 1-17 (volumes 1-3) of the manga and episodes 1-14 of the anime. Some events happen in different orders depending on the adaptation. This arc starts three days before the Index arc of A Certain Magical Index, and ends three days before the Index arc ends.
Mikoto Misaka leans on a rail while sipping a drink when she sees some thugs up to no good. She notices everybody else is backing away and ignoring the thugs and realizes they are suffering from Bystander Syndrome, believing the thugs are not their problem and someone else will deal with them. She sighs and says there's never a dull moment in Academy City.
On a bus, a tour guide tells the passengers, who are mostly prospective students and their parents, about Academy City. Suddenly, there is a bright flash and the traffic light malfunctions, nearly causing an accident.
Judgment member Kuroko Shirai chases down some thugs. She takes out a few of them, but the others run into an alley. She follows, only to find that Mikoto has already fried them into unconsciousness with her electricity.
As the pair walk to school, Kuroko scolds Mikoto, saying that civilians should not interfere with law-enforcement affairs. Mikoto brushes this off and comments that Judgment members like her are almost always late to crimes and disasters, so she might as well stop them herself. She horrifies her roommate by kicking a vending machine to get a free drink.
At Tokiwadai Middle School, there is a System Scan, where the student's esper powers are tested. Kuroko's test establishes that she can teleport a maximum of 130.7 kilograms in mass and a maximum of 81.5 meters in distance. She runs into Mitsuko Kongou, a Level 4 transfer student with the ability Aero Hand, which allows her to generate wind from her hands to launch projectiles at high velocities. Mitsuko makes fun of Kuroko's "weak" scores and says that she will soon become the Queen Bee around here with her superior powers. Kuroko warns her not to be too sure about that and points to Mikoto, who is testing how powerful her Railgun attack is by firing it at the swimming pool, with Kuroko pointing out that the Railgun is so powerful that they are running out of targets that won't get annihilated by it besides the pool. Mitsuko is amazed by Mikoto's power.
Note: In the manga and A Certain Magical Index, Mitsuko Kongou is introduced much later in the story.
Mikoto and Kuroko shower in the girls locker room and discuss their results. Kuroko suddenly teleports into Mikoto's stall and gropes her, causing Mikoto to beat her up.
At Sakugawa Middle School, Ruiko Saten sneaks up on her friend Kazari Uiharu and flips her skirt up. Uiharu yells at her and asks why she always does that even when they are in public, but Saten says it's just too fun to check her panties. Anyway, Uiharu is a member of Judgment, and her colleague Kuroko has invited her to meet her and her friend Mikoto. Uiharu invites Saten to join them. When they meet at a cafe, Uiharu and Saten get weirded out when they find Mikoto beating up Kuroko for being a pervert once again. After that awkwardness, the four girls start talking. Uiharu and Saten are amazed that despite being a Level 5, Mikoto is rather polite and down-to-earth instead of an arrogant snob like they expected. They walk around and find a crepe stand that is also selling Gekota toys (Gekota is a frog mascot marketed for kids). Mikoto goes into full Cuteness Proximity mode and wants a toy. Saten and Mikoto get into line, but when it is Mikoto's turn, there are no more toys left. She gets really sad, so Saten gives her the Gekota key-chain she bought.
As the four snack on crepes, they find a bank robbery going on. Kuroko and Uiharu go into serious mode and tell their friends to stay back. While Uiharu uses her laptop to scan the area and alert the other authorities, Kuroko charges into battle with the three robbers. The robbers laugh, asking what a little girl can do, and one of them demonstrates that he can shoot fireballs from his hands. Using a combination of teleportation and martial arts, she easily takes down the fire-user and one of the other robbers, but the third one runs away.
The robber grabs a little boy and tries to use him as a hostage, but Saten suddenly darts in and manages to pull him out of his arms. Enraged at her interference, the robber kicks her in the face, then jumps into a car and drives away. Kuroko prepares to pursue, but Mikoto says she's stepping in, for the robber has just made this personal. She pulls out a coin and uses it to fire a Railgun attack at the car, flipping it through the air and KO'ing the robber.
As the robbers are hauled off to jail, the boy and his mother thank Saten for saving him. Mikoto compliments her for being brave enough to step up and help the boy even though she is a Level 0 and has no powers.
Note: In the manga, Uiharu meets Mikoto and Kuroko alone. She wears a medical mask because she constantly has the flu. Mikoto decides to step in and stop the last robber for the petty reason that he bumped into her and made her drop her crepe.
One morning, Mikoto chases Touma Kamijou through the city until they reach a dead end in an alley. Panting, she smiles and says she's finally caught him. He tells her to wait a second, but she fires a blast of electricity. However, he stuns her by blocking the blast with his right hand. As she leaves the alley, Saten and Uiharu run up, saying they heard a loud noise coming from this direction. Mikoto laughs nervously. In the alley, Touma is gone, and the area is scorched black except for where he was standing.
Meanwhile, Kuroko showers, puts on lipstick, prepares some martinis, and dresses in sexy lingerie. She narrates that it's been a month since she and Mikoto have become roommates, and now is the time for them to finally consummate their "relationship". When Mikoto walks into their dorm room, Kuroko excitedly leaps toward her, but is forced to backtrack when she sees Uiharu and Saten are with her.
After Mikoto smacks her for being a pervert and forces her to get dressed, Uiharu and Saten look around the room and marvel at how luxurious it is. Kuroko fumes about the other two girls ruining the special day she planned, but then she gets a hilarious fantasy where Mikoto brought the two of them as witnesses as they confess their love. In this Imagine Spot, Mikoto and Kuroko reenact the ending for Casablanca.
Saten pokes around the room and finds Kuroko's underwear drawer. Uiharu asks what she thinks she is doing, but Saten claims she has every right to as a guest and friend. The girls are surprised to find Kuroko has incredibly risque underwear, but Kuroko says she doesn't see what the big deal is. Saten finds a pair of panties with a frog design on them, the kind a child would wear. Mikoto says those are hers, then angrily pinches Kuroko's cheeks and stretches them, asking why she has her panties. Uiharu and Saten try to calm her down and change the subject by asking to see their photo albums. Mikoto agrees and shows hers. The other three gush at how cute she looked as a young child and say her mom is hot. Saten is surprised, since she expected Mikoto to have been rich and raised as part of the social elite due to her Level 5 status. Mikoto explains that she wasn't always a Level 5; she started out as a Level 1 and gradually worked her way up. Upon hearing this, Saten gets a depressed and frustrated look on her face, but stops before the others notice. Uiharu says it's time for Kuroko to show her album, but she says she does not have one. However, Saten pokes around the room again and finds it. Kuroko desperately tries to stop her, but she opens it. Inside are several candid photos of Mikoto, including shots of her in the shower and up her skirt. Mikoto starts beating her up again, but Kuroko asks her if she even remembers what today is. Mikoto tries to think, then concludes that it has been a week since they met and became friends with Saten and Uiharu, causing Kuroko to Face Fault.
While Mikoto, Uiharu, and Saten eat snacks and chat, Kuruko sulks in the corner and drinks a canned red bean beverage. The can soon runs empty and she starts obnoxiously slurping it. Mikoto yells at her to cut it out, but Kuroko calls her out on not remembering that it's been a month since they were "bound together by the Red String of Fate" and starts theatrically crying. However, Mikoto starts beating her up again and reveals that Kuroko manipulated the system to make them roommates, fate had nothing to do with it. The intercom rings and a delivery man says he has "computer parts" addressed to Kuroko Shirai. Kuroko is relieved that the delivery company knows how to be discrete, but Mikoto asks where the parts are from, and the delivery man flatly answers that it's from a shop that sells herbs and aphrodisiacs. Enraged, Mikoto realizes Kuroko had been planning to drug her so that she could have her way with her. She fires an electric blast, but Kuroko teleports out of the room and the blast blows the door off its hinges. Kuroko laughs and explains that she can teleport fast enough to dodge her blast. Mikoto tries to attack again, but stops as her eyes widen in pure horror. The Tokiwadai Dorm Supervisor has arrived. Mikoto and Kuroko both drop their fight and try to act innocent, but she says that they used their powers inside the dorm, which is against the rules. Kuroko tries to explain that there were extenuating circumstances, but the woman suddenly snaps her neck before she can react (this franchise is normally realistic and doesn't use Toon Physics, but the Dorm Supervisor is an exception; when she snaps someone's neck, they are fine in the next scene). Terrified, Mikoto cowers and Uiharu and Saten hide. The woman says rule breakers will not be tolerated and must be punished.
The next day, Mikoto grumbles as the Dorm Supervisor ordered her and Kuroko to clean the empty school swimming pool. The pool is so huge that they've barely made any progress despite working all day. However, Kuroko is happy that she's spending quality time with Mikoto, and that Mikoto is sweaty, making her shirt partially see-through. She offers Mikoto a bottled drink, but she's not falling for it, she knows Kuroko laced it with aphrodisiacs. Kinuho Wannai and Maaya Awatsuki, two members of the swim team, walk up and ask what they are doing. They are Kuroko's classmates, and while she explains, Mikoto laments that the two have larger breasts than her despite being younger. The two are introduced to Mikoto and are in awe of her, having heard about how she helped foil a bank robbery a few days ago. Kuroko gets jealous when Mikoto, Kinuho, and Maaya start chatting and Mikoto accepts a bottled drink from Maaya. Kinuho demonstrates that she is a Level 3 with the ability Hydro Hand, control over water, and uses it to clean a small area of the pool. Kinuho and Maaya leave, promising to help them finish cleaning the pool after they do an exam. Kuroko starts crying, saying she's of no use to Mikoto and everybody else is replacing her, leaving Mikoto at a loss as to what to do.
Meanwhile, at a restaurant, Uiharu and Saten talk about Mikoto and Kuroko, wondering about Kuroko's queer tastes and about if Mikoto gave the present they bought together yet. Mikoto tries to calm Kuroko down and says she remembered something important that happened a month ago. On the day they became roommates, they roughhoused and ended up forced to clean the cafeteria as punishment. Ever since then, they've been friends. She pulls a present out of her bag and hands it to Kuroko. It's a t-shirt. Kuroko is stunned and they share a toast. However, Kuroko realizes too late that she drank her own spiked bottle and immediately falls under the aphrodisiac's effects. She poses provocatively and tells Mikoto that since they are in a pool, they should change into their swimsuits. Mikoto says it would be too much of a hassle to retrieve them, but Kuroko says she's already taken care of it and holds up Mikoto's swimsuit. Mikoto smacks her with her broom and points out her swimsuit was in her locked locker, but Kuroko points out locks can't keep out a teleporter. Out of nowhere, she teleports Mikoto's undergarments right off her. As Mikoto gasps and tries to hold her shirt closed, Kuroko laments that her underwear is so childish instead of sexy, but she notices they match her t-shirt. She starts running around chanting this, so Mikoto finally snaps and attacks her. Kinuho and Maaya come back, saying they finished their exam, but are stunned to find Mikoto savagely electrocuting Kuroko, demanding her underwear back. However, Kuroko just takes the shocks and gets more and more aroused. Kinuho and Maaya turn around and walk away, declaring, "Let Us Never Speak of This Again."
One day, Mitsuko Kongou takes a walk alone. She hears footsteps and looks around, but sees nothing. This happens a few more times and she gives a warning to whoever is doing that to cut it out. Suddenly, she bumps into something, but she can't see what she hit. She then screams and collapses as she's stabbed by an invisible stun gun. A girl stands over her, smiling.
Saten and Uiharu are on a bus to the School Garden, a sort of "mini-town" where normally, only students of elite schools like Tokiwadai are allowed. When the bus arrives, Uiharu is able to count down exactly when the rain will stop, citing Academy City's advanced technology. They are stopped at a security checkpoint, but are allowed in due to Kuroko's invitation. Inside, they are awed by how magnificent the area looks. Not only are there splendid gardens, but the buildings and streets have a European/Roman flavor. Saten looks at a clock tower and notices they are late for their meeting with their friends. She tells Uiharu to hurry, but Saten slips and falls into a puddle.
They meet Mikoto and Kuroko and go to a shower room, where Saten changes into a spare Tokiwadai uniform. Uiharu gets a little jealous because she wanted to try out a Tokiwadai uniform.
They walk together and send Saten's original uniform to the cleaners. The girl who attacked Mitsuko earlier eyes them as they pass her. The four go to a cafe, but Uiharu gets a call from Judgment. Annoyed, she and Kuroko leave for work. Mikoto tries to chat with Saten, but she goes to the bathroom.
Arriving at Judgment headquarters, Uiharu and Kuroko meet their superior, Mii Konori, and complain about having their planned day ruined, but she scolds them and says this is serious. In the past day, six Tokiwadai students have been knocked out by stun guns. Back in the cafe's bathroom, Saten notices the door seem to open and close by itself. Back with Mii, she tells the two that the six victims were all at least Level 3, so they believe the attacker was very powerful. Saten is zapped by the stun gun and passes out. Mii tells the two that the attacker does something horrible to the victims while they are unconscious, and shows them pictures, warning that they are not for the faint of heart. Mikoto asks Saten what's taking so long and enters the bathroom to find her unconscious.
Saten is laid to rest on a couch while Mikoto is filled in on the situation. Apparently, the attacker mistook Saten for a Tokiwadai student because of her borrowed uniform. They are not sure what the attacker's motive is, but can deduce that she is invisible to human eyes, but not to mechanical ones. They are shown a recorded interview Mitsuko had with an Anti-Skill officer after her attack. She is very embarrassed and covers her forehead. She insists that she did not see her attacker, but the officer shows her security camera footage of the attacker (her back to the camera) right next to her.
They know of a few espers who can turn invisible, but they all have alibis and they don't show up on camera. A pigeon flies by the window, which Uiharu notices, but Kuroko doesn't. This gives Mikoto an idea, and they check a database for esper abilities until they find Dummy Check, an ability that erases oneself from perception. This ability belongs to a girl named Miho Jufuku. However, she is only a Level 2, and her ability is supposed to not be refined enough to sneak up on so many people so easily. Saten wakes up and they try to console her, but suddenly burst into laughter. She asks what's so funny, and she's horrified to find her attacker drew Big Ol' Eyebrows on her while she was unconscious. She looks at the image of Miho and confirms she was the one who attacked her. They ask how she is so sure, and she explains that although she couldn't see her, Miho's reflection still appeared in the bathroom mirror. Saten chuckles creepily and says it's payback time, and demands Uiharu spring into action.
Uiharu comments that what Saten wants her to do is technically illegal, but Kuroko gets a phone call from Judgment saying it has been approved. Uiharu hacks to the security grid and her computer shows the screens of 2,458 security cameras in School Garden. Now, Miho can't hide. Saten tells them to keep her posted and exits the room. Mikoto, Kuroko, and Uiharu start using process of elimination to narrow down the areas where Miho will likely be.
Kinuho says goodbye to Maaya and walks away from her. Miho sneaks up on her with her stun gun, but Saten, wearing a baseball cap to hide her eyebrows, interrupts her. Shocked, Miho runs away, and Saten gives chase, following instructions Uiharu gives her via an earpiece. Kuroko suddenly appears and kicks Miho, making her visible. Kuroko says she's under arrest, but Miho activates her power again and runs away. Kuroko and Saten pursue her using Uiharu's directions.
Miho runs into the park and is so exhausted that her power deactivates and she becomes visible. Mikoto walks up and says it's over. Miho suddenly stabs her with her stun gun, but Mikoto points out that electricity has no effect on an Electromaster such as herself, then shocks Miho unconscious. The other three arrive. Saten pulls out a marker and says it's payback time. She lifts Miho's bangs, only to find that she has natural Big Ol' Eyebrows. The girl wakes up and shamefully covers her forehead, telling them to go ahead and laugh, just like "that guy" did. However, they have no idea who she's talking about.
She explains. She used to have a boyfriend, whom she though was her one true love. One day, he left her for a Tokiwadai student, and said that he's leaving her because her eyebrows were ugly. Therefore, she decided to take revenge by giving every Tokiwadai girl she can find eyebrows like hers. The girls comment that has to be the stupidest reason they have ever heard. However, Saten tells her not to sell herself short. Her eyebrows are not ugly, in fact, she thinks they're cute. This attempt to cheer her up works a little too well; Miho blushes and stares at her. Kuroko calls Saten an idiot, and she realizes what she just did and freaks out.
An Anti-Skill wagon arrives to take Miho to prison. After all, she did assault seven girls and traumatize them. Miho steps into the wagon without resisting. She turns to Saten and asks if she will write to her. Saten says yes, and Miho sits down, blushing and satisfied. The wagon drives away.
Mikoto wonders about how advanced Miho's power was. She proposes that Miho's database entry was inaccurate, but Kuroko claims that that's ridiculous; the database is foolproof.
Later, Saten throws a tantrum. According to Mii, the marker that Miho used won't wash off for about ten days. Uiharu suggests she just wear the baseball cap until it's time, but Saten angrily tears a pillow apart and says she should have scribbled all over Miho's face while she was unconscious.
Note: Miho Jufuku is an anime-exclusive character, so this adventure is anime-exclusive.
One day, the girls start telling ghost stories, but Saten tells a Mundane Ghost Story about a woman with an uncontrollable urge to strip in public. The others are underwhelmed, with Mikoto saying the woman is not scary, just a pervert. Uiharu pulls up on her laptop a site that lists urban legends, which is where Saten got her story from. The urban legends include:
Kuroko scoffs and tells them to stop looking at useless sites. She deals with facts, not make-believe. Mikoto agrees with her. Saten calls them spoilsports; where is their sense of adventure? She reads another urban legend about a boy who can negate other people's esper powers. Kuroko says that has to be the most ridiculous story yet. However, Mikoto grows nervous and silent. After all, she knows this story is true.
While shopping, Mikoto has a flashback to the day she met Touma. She was taking a walk when she got surrounded by lecherous thugs. Of course, she was unconcerned because of her powers. She notices the citizens around them turning away and minding their own business. She muses that she doesn't blame them; they don't want to get hurt, and besides, only an idiot would try to help a complete stranger... Suddenly, Touma walks up, calling her his sister. He takes her hand and tries to leave, but she asks him who the Hell he is. He groans and asks why she didn't just play along, he was trying to save her. The thugs angrily confront him and say they won't tolerate his interference in their affairs. He tells them they should be ashamed of themselves. Why are they ganging up on and sexually harassing a little girl; are they pedophiles? Insulted at being called a little girl, Mikoto zaps them all. The thugs are all roasted unconscious, but Touma holds his right hand out and is unharmed, amazing her.
The flashback ends and she walks around, wondering why her shocks don't work on him. She then spots him talking to a woman. Apparently, the woman can't remember where she parked her car and he's trying to help her. When he sees her, he displeases her by calling her "Biri Biri" instead of her name. Mikoto challenges him to a fight, but he says he is busy and tries to get her to help the woman instead so he can get back to what he was doing. Suddenly, the woman takes off her shirt. They freak out and ask what she is doing, and she matter-of-factly says it is too hot, so she's cooling off. Touma grabs her shirt and tells her to put it back on, but the people around them see them and assume that Touma attacked the woman and pulled her shirt off. He tries to explain, but has enough, hands the shirt to Mikoto, and runs away from the angry people. She tries to follow him, but the woman tells her not to leave, or she'll lose track of her shirt. Annoyed, Mikoto tells her to get dressed.
Mikoto and the woman sit, and she tries to ask her why she doesn't seem to have any sense of shame. She then remembers the story Saten told. Kuroko calls her, saying the girls are having tea and they would like her to join them. Mikoto tells them she's found a weirdo who strips in public. Saten and Uiharu are with Kuroko and point out it's just like Saten's story. The woman asks who she's calling a weirdo, and Mikoto hangs up and apologizes. Kuroko is concerned, and Saten starts mischievously suggesting the woman is dangerous.
The woman pulls out some canned drinks and hands one to Mikoto. She looks at the label and finds it's spicy. The woman explains that drinking something hot and spicy actually cools you down, and is nutritious. Mikoto says she'd rather drink something cold. The woman apologizes and explains that she's been so caught up in research that she's been basing all her decisions on logic and not on how people feel. Mikoto asks if she is a scientist, and she explains that she specializes in AIM (An Involuntary Movement), the energy that all espers emit when they use their powers. Impressed, Mikoto says this must mean she knows a lot about various esper powers, and the woman confirms this. Mikoto asks if there is an esper power that can negate other esper powers. The woman asks her to clarify, and she says there is a person who seems to be immune to electricity. The woman suggests this person can draw electricity away like a lightning rod, but Mikoto says it didn't seem like that. The woman asks if this person is an acquaintance of hers, and Mikoto gets embarrassed. A little boy trips and spills his ice cream cone on her skirt. The boy apologizes, but the woman tells him it's no big deal, then takes her skirt off, making him blush. The onlookers ask what is going on, and Mikoto drags the woman away, asking what is wrong with her.
Kuroko tries to call Mikoto, but can't reach her. Saten starts bragging about how the story she told ended up being true. Uiharu looks up the urban legend site and finds a reference suggesting that the stripper lady's "condition" might be contagious. Kuroko starts freaking out, not wanting Mikoto to disgrace herself by stripping in public. She begs Uiharu to find a way to undo the "curse", and they beg her to calm down.
In a bathroom, Mikoto washes the woman's skirt and dries it under the hand dryer. The woman, in a stall, apologizes for putting her through so much trouble. As she gets dressed, she asks Mikoto to thank the boy who helped her earlier if she finds him. Incredulous, Mikoto says he tried to force her to take his place and then abandoned them. The woman says it wasn't his fault, and he was a true gentleman, the only person who didn't ignore her when she was asking for help with finding her car. The woman says she could tell Mikoto has a crush on him. Mikoto turns red and says that's not true. The woman says she's just acting Tsundere for him (in the English dub, she says "playing hard to get"). Mikoto gets so flustered that she releases a wave of electricity that causes the mall they are in to suffer a blackout. As an alarm sounds, Mikoto grabs the woman and runs away.
Late in the afternoon, they finally find her car (by the way, it's a Lamborghini Gallardo). The woman thanks her for all her help and drives off. Annoyed, Mikoto asks how anybody could forget the parking lot they parked in. She says it's all that boy's fault. When she finds him... her thoughts are interrupted when she sees Touma nearby. He's complaining because he waited in line for two hours just to buy eggs, but now they're broken. She yells at him for forcing her to deal with that weirdo stripper, but he says he's poor and may have to go hungry for a while, something a rich girl like her could never understand. She starts listing the crazy stuff she experienced with the woman, then remembers how the woman said she has a crush on him and blushes. He asks what's wrong, and she tells him to forget it and fight her. He asks what the point is, she's never been able to hurt him. She says he never tries to hurt her, so he's never beaten her either. He glares at her, making her gulp, and says fine, they'll have a real fight so that they can finally settle this and she'll leave him alone.
As night falls, they go to an Artificial Riverbank, where they can go all out without harming anybody. Mikoto fires an electric blast, but Touma blocks it with his right hand. She says she's thought of some new tricks and magnetically gathers the iron sand around her into a sword. A leaf falls on the blade and splits in half. Horrified, he claims weapons are against the rules, but she says she made it with her powers. She explains that the sword's incredible cutting power comes from the fact the sand particles are vibrating like a chainsaw. She attacks and he ducks and rolls out of the way, then runs. She says it's no use and extends her blade, making it flexible as well, then swings it at him. Fortunately, he catches it with his right hand, causing it to fall apart into sand again. Undeterred, she magnetically gathers the sand into a cloud that moves toward him. He backhands it away, but she uses this distraction to get behind him and grab his right hand with her own. She says she has him now, he may be able to block electricity flowing through the air, but he surely can't block current coming directly from her. She tries to zap him, but nothing happens and no electricity will come out of her. She asks what is going on. He glares and raises his left fist, and she cowers. He's incredulous, then suddenly lets go of her hand and falls to the ground, pretending to have been electrocuted. He "weakly" says that she won. Unfortunately, she's not fooled for a second, and angrily releases several blasts that he dodges. He says he can't bear to hurt a girl who looked that scared, and she denies that she was. He says she was, and imitates the face she made. She doesn't take this well and fires some huge blasts. He runs away and yells that if any of them had scored a direct hit, they would have killed him. She gives chase and says they wouldn't have worked on him anyway. He says it doesn't matter whether they would have worked or not, what kind of person would casually use lethal attacks? She screams that he's the only person she can use full power on without risking him being killed. She chases him for several hours.
Exhausted, she comes home after losing track of him, but she finds the room empty. She starts changing into her pajamas, but finds Kuroko under the bed, with a pair of panties on her head. Kuroko has apparently gone off the deep end, and tells her she needs to put panties on her head to break the curse of the stripping lady. Mikoto beats her up.
In a poorly lit room, the woman looks Mikoto up with her laptop. She comments on how the person who helped her was the #3 Level 5 and says this is interesting. Mikoto sleeps soundly with Kuroko bound and gagged on the floor.
In a flashback, we are shown when Kuroko and Uiharu first met as young Judgment trainees. Uiharu was doing poorly in the physical fitness tests, but Kuroko encouraged her not to give up.
In the present, the two are scouting locations to install new security cameras when they spot some thugs trying to steal a car. Uiharu tells her partner to wait for backup, but Kuroko charges straight at them, overconfident in her abilities. One of the thugs manages to blindside her and knock her out. Uiharu tries to help her, but they knock her down and escape. Kuroko wakes up and is disappointed in their failure. Uiharu says it was her fault for jumping in without thinking, but Kuroko refuses to admit this and blames her for being so weak. They argue and say they never want to see each other again.
Saten enters Judgment's office, much to Mii's chagrin, saying this isn't a social gathering spot. Saten wants Uiharu to help her with her homework. Saten finds her and flips her skirt, but Uiharu doesn't react, much to her shock. Mii explains that she's really upset because of her and Kuroko's little tiff. Saten asks how the two became friends, and Mii decides to tell her...
Back in Tokiwadai, Kuroko is very grumpy and restless. Mikoto learns about the fight she had with Uiharu and asks how they became friends. Kuroko decides to tell her...
One day, Mii and Kuroko were on patrol. Kuroko asks why she's still relegated to odd jobs and patrols even though she's proved her worth as a fighter and had good grades. There are officers of similar age to her. Mii says her training results are excellent, but she still needs to work on her attitude. Kuroko doesn't understand what she means. They go to the bank and Mii tells her to wait while she withdraws some cash.
As Kuroko waits in the lobby bored, Uiharu walks in, saying she's still rather new to the city and is trying to get the lay of the land. They chat. Since they have not yet met Mikoto Misaka, Kuroko ironically says she heard the #3 Level 5 is a total snob. Mii walks back and points to a man who's acting suspiciously. She uses her esper ability, X-Ray Vision, and is horrified to find that the man is fingering a gun in his bag. Mii says she will warn the employees while they prepare to evacuate the customers. Kuroko asks why they don't just attack the man, but Mii tells her not to be stupid and just do what she asks. Mii walks over to an employee and asks her to call Anti-Skill, but the man suddenly draws his gun and fires a shot into the ceiling, telling everybody not to move. Suddenly Kuroko jumps in and takes the man down with a kick and judo throw. She boasts that that was easy, but then another man draws a knife and takes Uiharu hostage. The knife-wielder mocks his accomplice for getting knocked out by a little girl, but now he's holding all the cards. He's right, Kuroko and Mii will not dare risk Uiharu's life.
The manager presses an alarm that closes the bank's metal shutters, trapping everyone inside. Mii gets annoyed by this faulty security measure. A security robot appears and attacks the robber, but the man calmly backs away and reaches into his pocket. Mii notices this, but Kuroko doesn't and charges. Mii pulls her out of the way just as the man throws something that blows up the robot. Unfortunately, Mii gets hit in the back by shrapnel. Before she passes out, she berates Kuroko for always charging in without thinking. The robber, still holding Uiharu with one arm, starts beating Kuroko up. She takes the blows and realizes Mii was right, and this is all her fault. She manages to touch Uiharu and teleport her outside. She explains that at this stage of her development, she can only teleport others and not herself.
The robber realizes Kuroko's plan is to stall until Anti-Skill shows up, but he boasts that he's not as trapped as she might think. He explains his esper ability is called Equal Speed, and demonstrates by throwing a marble at the metal shutters. The marble, despite flying through the air so slowly, punches a hole right through the metal. With his ability, anything he throws will never lose momentum until he stops concentrating on it. He throws a few more marbles until the hole becomes wide enough to walk through. He orders her to use her power to retrieve the bank's money and in exchange, he'll let everybody live. He then proposes they become a team, with their combined powers, they'll be unstoppable. She refuses. Outside, Uiharu begs for someone to help them, but all the passerby just ignore her. However, Mikoto, who was taking a walk, notices her.
The robber, angered that Kuroko spurned his offer, throws several marbles at her, leaving no room to dodge. At the last second, Mikoto fires an electric blast through the hole that burns the marbles to dust. Everybody is stunned and nobody saw where that miraculous blast came from, but Kuroko recovers enough to attack and take the robber down.
The customers cheer and Mikoto walks away, while Anti-Skill finally arrives. As Mii and Kuroko get treatment for their injuries, Kuroko declares that she's learned her lesson, and she will remember that she is part of a team instead of trying to do everything herself. She and Uiharu shake hands as partners.
As the story ends, Kuroko realizes that she had forgotten her lesson and vows not to forget it again. She finds Uiharu and they make up. The car thieves have been identified and they decide it's payback time. They run off, though Uiharu quickly complains because she's still not very athletic.
One day, in the bushes somewhere, a teddy bear implodes and then makes a tiny explosion. The passerby assume it is just a firecracker.
Kuroko is frustrated because these little explosions have been going on throughout the city. Most people assume it's just a prank, but they could become dangerous. According to satellite surveillance, aluminum and accelerated graviton particles are found in each explosion. The database shows an esper girl named Katabira Kushino with the ability Synchrotron, making aluminum explode by accelerating graviton particles. However, she has been ruled out as a suspect because she has been in a coma for quite a while now. Mikoto offers to help, but Kuroko scolds her and says to leave it to Judgment and Anti-Skill. She makes Mikoto promise to not try to seek the culprit because she is a civilian and to call the authorities if she does find him or her. She then tries to make her promise to wear sexier clothing and get rid of her childish interests like Gekota. Mikoto gets angry and says that has nothing to do with their situation.
Later, Mikoto has lunch with Uiharu in a restaurant. Mikoto complains about how overprotective Kuroko is and how she thinks Mikoto can't handle situations just because she's a civilian. Doesn't she remember how powerful she is? Uiharu tries to say Kuroko just cares about her. The two start discussing the case. At first, certain aluminum things like trash cans were what was exploding, but now it's toys and bags with scraps of aluminum stuffed in them. Uiharu's order of a jumbo parfait comes in and she tries to dig in, but Kuroko walks in and berates her for slacking off. They're on an investigation of the explosions. Uiharu begs her to wait until she finishes, but Kuroko angrily drags her away. Mikoto protests, but Kuroko says Judgment is serious business and a civilian like her can never understand. As the two leave, Mikoto complains about Kuroko's high and mighty attitude, but notices Uiharu left her Judgment armband behind.
She takes the armband and tries to return it, but loses track of them. Suddenly, Mii walks up and mistakes her for a Judgment new recruit because of the armband, telling her to get to work. Mii doesn't know who she is, and Mikoto decides this is her big chance to prove she deserves to fight just like Judgment members.
However, Mii hands her a broom and tells her to start sweeping. When not fighting crime, Judgment does community service. Mikoto finds this degrading. When some jerk throws his trash on the ground and tells her to sweep it up even though there was a trash can right next to them, she loses it and beats him up. Mii smacks her.
Meanwhile, Uiharu tries to find her armband, but can't. Kuroko scolds her for being so careless. They find a little girl crying and ask her if she is lost. Mii scolds Mikoto for losing her temper. She declares that she will do a better job.
Mikoto and Mii start helping people, but Mikoto keeps tripping up. Later, the two snack on crepes on a park bench. Mikoto says she had no idea being in Judgment was so hard. Mii admits that she used to screw up all the time when she was a recruit as well. Mii gets a call saying that a little girl's bag was stolen by a dog. Remembering what Uiharu said about the explosions, Mikoto worriedly says they have to find the bag now, confusing Mii.
The two start looking around, but have no luck. Back at Judgment's office, Uiharu sits with the sleeping little girl on her lap while Kuroko calls other officers asking if they have seen the dog with the bag. Saten walks in and teases Uiharu, asking if the girl is her daughter. Uiharu fills her in on the girl's missing bag. Saten comments that they seem to be going overboard with such a small thing, but Uiharu says the girl's parents are unavailable and the bag has all her stuff, so they are all she has. Saten understands.
While searching for the bag, Mikoto sees a glasses-wearing man listening to headphones accidentally bump into some thugs. They angrily start beating him up. Mikoto chases them away and tries to tend to the man, but the man ungratefully yells at her for not helping him sooner and storms off. Annoyed, she asks what his problem is. Mii walks up and says there is one place they haven't looked in.
They come to a children's playground. Mikoto is immediately surrounded by them, curiously asking her questions. To her embarrassment, one of them lifts her skirt and gets surprised at how she wears shorts underneath. She sees the dog with the bag and gives chase. She eventually resorts to zapping it with a tiny jolt to make it let go, but the bag flies through the air. She panics and leaps up to catch it, landing in a fountain. Mii thanks her for her hard work and takes the bag, scaring Mikoto as she thought the bag was going to explode any minute, and Mii asks what she is talking about.
An exhausted Mikoto can't believe she was on a wild goose chase as she thought the bag was one of the bombs. Kuroko, Uiharu, and the girl (according to the credits, her name is Kana Hazamaya) arrive to retrieve her bag. When Kuroko and Uiharu see Mikoto, they are shocked. Mii is confused by their reaction, and they finally explain who she is. Mii gets shocked that she was hanging out with the #3 Level 5 all this time. Mikoto returns Uiharu's armband and apologizes for impersonating an officer, but Mii says it is all right. Kana shyly thanks Mikoto for finding her bag. At this, Mikoto smiles, deciding that although her day was terrible, making this adorable child happy was Worth It.
In their dorm, a tired and sore Mikoto tries to relax. Kuroko says she hopes she learned her lesson about leaving things to the professionals. Mikoto says after spending a day in her shoes, she's gained a new understanding of her. At this, Kuroko suddenly strips and starts hitting on her, ranting that they've made a new connection. Mikoto angrily tells her cut it out. The Dorm Supervisor bursts in (crushing Kuroko with the door) and tells them to keep it down.
Two Judgment members enter a small store and tell everyone to evacuate. The manager asks what is going on, and the female officer explains that graviton acceleration has been detected in this area, so an explosion is eminent. A girl trips and hurts her ankle. The male officer is horrified to see a toy near her imploding and charges. The toy explodes. The female officer shields herself and the manager with a riot shield, then they find that the male officer covered the girl with his own body. He's battered, but alive.
Note: The male officer and the girl he saved do not appear again in the anime, but in the manga, they have a small appearance in the Sister's arc. They apparently started dating after this incident.
One week later, Judgment is on edge. The explosions are happening more frequently and are getting stronger each time. Mii Konori tells her colleagues that there have been no leads, but they must solve this to prevent more victims.
Meanwhile, the ungrateful man who Mikoto helped earlier gets mugged by some thugs. He doesn't try to fight back and simply glares at them. Throughout the ordeal, he keeps his headphones on.
While hanging out, Kuroko yawns and says she's been up all night working on the bombings case. Mikoto tells her not to push herself too hard, but Kuroko ruins the tender moment by hitting on her again. A bus passes by, bearing the headphones man.
At school, Saten asks Uiharu if she wants to go shopping at the mall after class, but she says she's part of the investigations, disappointing her.
After school, the headphones man starts walking home, but gets accosted by the people who mugged him earlier, saying they want more money. The man says they haven't returned the cash he gave them earlier. Annoyed, they tell him not to be a smartass and beat him up, taking the remaining money in his wallet. One of the thugs says they should leave before Judgment arrives. They leave, but their leader laughs and says they will never be caught because Judgment never shows up on time. Alone, the headphones man growls and blames Judgment for his problems, swearing that he will make them pay.
Kuroko and Uiharu go over everything they have on the case. The strength of the explosions suggests a Level 4, but the database doesn't show anyone with a similar ability.
Mikoto runs into Saten, who's depressed that she couldn't hang out with Uiharu today. Saten muses that her three friends are so amazing, and she wishes Level Upper was real. Mikoto asks what that is, and Saten says it was part of the urban legends website, a device that supposedly increases esper powers. If it were real, she'd use it to get a power and be useful to the others.
Kuroko gets a call from Mikoto asking her when she and Uiharu are free. They're off duty right now, so Mikoto suggests the four of them hang out at the mall. Kuroko decides to do a little more investigating. Meanwhile, the headphones man carries a frog doll in one hand and a spoon in another. He spots the girls walking by and sneers when he sees Uiharu's Judgment armband.
Mikoto, Uiharu, and Saten go to the underwear section. Saten tries to persuade Uiharu to buy a sexy pair, but she refuses because she knows Saten just wants to flip her skirt. Mikoto moves toward some kiddy style pajamas, but gets embarrassed when the others see and awkwardly tries to cover up her interest. She manages to grab the pajamas when the others move to the swimsuit section, but runs into Touma.
She turns red and asks what he is doing here, but he says he can go where he wants. Kana walks up, calling Touma "big brother", and is happy to see Mikoto again. Surprised, Mikoto says she didn't know he had a sister, but he says he doesn't. He just found Kana wandering around the mall and decided to chaperone her. Kana says she wants new clothes to be stylish. Mikoto smiles and says she already is. Touma snarks that Kana is a lot more stylish than her. Angered, Mikoto challenges him to another fight, but he shames her by asking if that's all she thinks about, and if she would really do this in front of this child and indoors. He and Kana walk away. Uiharu and Saten walk up and ask why she was yelling. She says it was nothing and goes to the bathroom. After freshening up, she complains that Touma really irritates her. She spots the headphones man carrying the frog doll and gets excited, but stops and frowns when she realizes it is not a Gekota doll.
Kuroko works with Mii on the case. They realize that the explosions tend to happen where Judgment members hang out. Suddenly, their satellite surveillance reveals graviton acceleration in the mall.
Kuroko frantically calls Uiharu with this information. Uiharu tells her friends to help her evacuate the mall. The PA system warns everybody to get out, and the girls direct everybody to the exits. Kuroko starts teleporting toward the mall in bursts.
Touma runs up to Mikoto, frantically saying that he and Kana got separated and she is not outside. Kuroko calls Uiharu, telling her that the bomber seems to be targeting Judgment members, so she's next. Suddenly, Kana walks up to her, oblivious to everything that is happening, and happily shows off the cute frog doll that a man in glasses gave her. Uiharu sees that the doll is slowly imploding and realizes it is the bomb. She snatches it and throws it to the side, but it doesn't fly very far. She grabs Kana and shields her with her body. Mikoto decides to knock the toy away with her Railgun, but she stumbles and drops her coin. Just as it seems that all is lost, Touma charges up to the toy and holds out his right hand. The toy explodes, but the explosion doesn't reach them. Since Uiharu was covering Kana, Mikoto is the only one who sees this.
The explosion rocks the mall and everybody is worried, including Saten. The headphones man walks into an alley and gloats. He is Hatsuya Kaitabi, the Graviton Bomber, and he's glad that he blew everybody up, including that Judgment girl (Uiharu). Mikoto sneaks up on him and kicks him in the back. She says she's glad she found the bomber so she can finish this. He tries to deny it, but when she explains that nobody was hurt by the explosion, he angrily rants that he used full power in that blast, trapping him. Now that pretenses are off, he pulls a spoon out of his backpack and tries to throw it at her, but she knocks it away with electricity. His power is useless, because aluminum is a metal and her electromagnetic powers can control metal and knock it away. He moans that since she's a Level 5, it's only natural that he can't beat her, and complains that everyone's a bully, with those who have stronger powers picking on those who are weaker. Annoyed, she punches him in the face, flooring him, then walks away. Kuroko appears and arrests the man, saying his logic is flawed and people who would use powers or lack thereof as an excuse to hurt others sicken her. Mikoto started out as a Level 1, and worked her way up to Level 5 through hard work. And even if she were still a Level 1, she'd still try to stop him.
Kuroko looks at the explosion site in wonder. Uiharu and Kana walk up and say they are okay. Kana says Mikoto saved them and she is the greatest. As Uiharu plays with the girl, Kuroko muses that while she has no doubts that Mikoto saved them, she has no idea how she could have blocked the explosion, even with power over electricity. Later, Mikoto walks away from the mall, staring at her bruised knuckles from when she punched Hatsuya. Kuroko hugs her from behind and thanks her for saving their friends. Mikoto nervously plays along. Kuroko offers to "reward" her with a massage or bath. Of course, Mikoto says it's not going to happen.
The next day, Mikoto walks to the vending machine in the park and muses about the previous day. Touma walks up, humming a certain tune, and stops annoyed when he sees her. She asks why he did not stay and explain that he was the one who blocked the explosion. If he had, he would have been praised as a hero. Honestly confused, he says that as long as everybody is safe, who cares who did the saving? He walks away, humming a certain tune. Irritated, she starts kicking the vending machine several times and screams that he's driving her crazy with his idiocy.
Saten sits in class while the professor drones on about Personal Reality. Saten looks at Uiharu's empty seat and muses on how she caught a fever and had to skip school. The professor calls on her and asks what he was just talking about. She cannot, but the class bell rings. The professor dismisses the class and tells her to pay attention next time. She stays behind to copy the notes on the broad, musing that knowing about Personal Reality is part of the key to obtaining esper powers.
Mikoto and Kuroko walk together and discuss the Graviton Bomber case. When Hatsuya was arrested, they tested his level, but he was found to be a Level 2, which doesn't make sense because that would mean he shouldn't be able to make such powerful explosions. They stop at a food stand and get some ice cream. Kuroko listens to some wind chimes and says that she feels cold for some reason. Mikoto says it's probably synesthesia and explains that some senses can stimulate others, like how colors like red and orange can make you feel warm and colors like blue can make you feel cold. They take bites out of their treats and both get brain freeze.
Saten joins them and gets some ice cream. She gets brain freeze as well, but says that even though she gets it a lot, she will still eat it. She notes that she has lemon ice cream and Mikoto has strawberry, and asks if she can have some. To Kuroko's shock and envy, Mikoto spoon-feeds Saten some of her ice cream, and Saten spoon-feeds her in turn. Kuroko asks Mikoto if she can spoon-feed her, but Mikoto says there's no point because they both have strawberry.
- Amplifier Artifact: The titular Level Upper. It's a sound file that uses synesthesia to manipulate all five senses at once, working as a poor-man's Testament to stimulate the brain and boost esper powers. Eventually, the user falls into a coma and becomes part of a network of living minds.
- Bystander Syndrome: The citizens of Academy City have a tendency to ignore people in trouble.
- The Cavalry Arrives Late: Judgment and Anti-Skill are almost always late to crimes and disasters, even Kuroko, who can teleport.
- The Dreaded: The Tokiwadai Dorm Supervisor is feared by all, now matter how powerful they are.
- The Greatest Story Never Told:
- Before they officially met, Mikoto saved Kuroko's life from the bank robber who had the ability Equal Speed, then walked away without anybody seeing her.
- Mikoto is the only person who knows that Touma was the one who saved them from the Graviton Bomber's explosion.
- I Just Want to Be Special: Pretty much everyone who uses the Level Upper file, to varying degrees. The Social Darwinist nature of Academy City encourages higher-level espers to look down on lower level ones, so it was more than just Level Zeroes who downloaded it.
- Indirect Kiss: Mikoto and Saten spoon-feed each other ice cream.
- Our Angels Are Different: Chronologically, the angel birthed from the Level Upper network is the first angel we see (and the second by publication order—the angel from Angel Fall was introduced first). It is both feral and childlike, carrying the rage of the ten thousand espers who created it, and capable of wielding all their powers to deadly effect. It's completely immortal until the network is shut down, as well.
- Never Be a Hero: This is Kuroko's firm belief that only law enforcement officials like herself should deal with criminals. Mikoto doesn't care what she thinks.
- Recognition Failure: A lot of people don't recognize Mikoto on sight.
