Mugino Shizuri

Mugino Shizuri (麦野 沈利) is a recurring character in Toaru Majutsu no Index and Toaru Kagaku no Railgun. She is the 4th-ranked Level 5 and is the leader of ITEM, a mercenary group in the Dark Side of Academy City. Mugino plays an antagonistic role to the 3rd-ranked Level 5 Misaka Mikoto in Toaru Kagaku no Railgun and is the archnemesis of Hamazura Shiage for most of her run in the original Toaru Majutsu no Index. She is relentless in battle, and combined with her destructive powers, makes her a very dangerous opponent to face.

After SCHOOL, led by Kakine Teitoku the 2nd-ranked Level 5, constantly one-ups ITEM during the course of factional war on October 9, Mugino takes a dark turn to the worst in her blind desire to take revenge, resulting in the death of Frenda Seivelun by her own hands, an action that will haunt her afterwards, and the destruction of ITEM. As she requires Takitsubo Rikou for her vengeance, she instantly becomes at odds with Hamazura Shiage, whom she later transfers her wrath to. His struggle against her and the Dark Side of Academy City in order to protect Takitsubo allows him to grow into a heroic character in the series.

After the events of World War III, Mugino Shizuri reconciles with the remaining members and reforms the group and goes on the path of rehabilitation. The organization becomes the only known faction from the Dark Side of Academy City that fought in the factional war on October 9 to not have been disbanded after the war.

Appearance
Mugino is a girl with a tall and slender figure. She has soft tea-colored hair. She has a knack for stylish clothing. Indeed she has been designed by Haimura to look like a model. Shiage noted that originally, from all the girls of ITEM Mugino Shizuri was the most beautiful and endowed with both style and grace fitting for an ojou-sama. Despite this, Mugino can also be practical, wearing shorts underneath her skirt. However unlike Misaka Mikoto, Mugino does not always wear them, as shown when Last Order sees that she is wearing panties. In Toaru Majutsu no Index she wore a bright short sleeved coat with a belt and checkered pattern ascot or cravat. She wore yellow stockings and sweater underneath. After her defeat at the hands of Shiage, the injuries she suffered would scar her face, take away her right eye, and destroy her entire left arm from the shoulder down. After World War III, one-third of her face was artificially treated with cosmetics and her missing eye and arm replaced. By the time of Shinyaku Toaru Majutsu no Index she begins wearing jacket over a shirt with a bolo tie, and then underneath a camisole. She now wear pants, belt, and boots.

In her appearance in Toaru Kagaku no Railgun, she wears a violet dress with shorts, along with black thigh high socks and white boots.

Personality
Mugino Shizuri has a mature appearance compared to the other girls in her team. Indeed, she acts like the big sister of the group, which works well with her position as leader of the organization. As the leader of ITEM, she cares for the utility of her teammates and would not hesitate to dismiss them when they get in the way, such as when she dismissed both Frenda and Takitsubo as they would only get in her way in taking down Mikoto, as well as the time when she belittles Shiage's shouting to himself that he once was the leader of Skill-Out. She praises those who are worthy of her praise, like Frenda and Takitsubo for their hard work, as well as Shiage when he showed his skill in lock picking. She, however does not tolerate incompetence or idiocy, which she responds to varying degrees, such as frustration when Shiage accidentally sends porn to ITEM's cellphone, to anger as Frenda has been subjected to several times. She can also be quite blunt, as exemplified with her lack of tact to the half-asleep Fremea Seivelun when she tried to explain that she killed her sister.

Despite what her appearance may suggest, in missions she is willing to kill other people. Moreover, she is a relentless person when it comes to victory, unable to let go of her quarry to the point of irrationality and the damage she is doing to others. This is especially prevalent if her quarry has embarrassed or has defeated her, in which her need for revenge just drives her. An example of this is her drive to defeat SCHOOL eventually leading to the destruction of ITEM, and especially her pursuit of Hamazura Shiage after defeating her twice to Russia in a midst of global war. Hamazura Shiage surmises this part of her in their first fight thusly:
 * "You’re the kind of person that can’t stand it when you can’t complete a video game without 100% accuracy. If you fuck up even slightly, you fly into a rage and won’t accept it even if you complete the game."

Further emphasizing her radical behavior, he states, continuing in his use of a video game metaphor, if she isn't able to get 100% accuracy she instead goes for a high score to compensate. An example of this was her failed attempt at killing Misaka Mikoto and instead letting her go after discovering she was trying to stop the Level 6 Shift in order to see her suffer against the Dark Side of Academy City instead.

Despite her dark nature, she truly cared for the members of ITEM. She regrets killing Frenda, visiting her grave and trying to continue living her life as a testament to keeping Frenda's memory. Indeed, she doesn't take kindly to anyone making light of Frenda's legacy such as being used to trick her. Although, this is likely an extension of her growth as a person after the war. In Shinyaku Toaru Majutsu no Index Mugino's personality has shown a slight change. When she meets and speaks with Last Order for a short while, she is far kinder and more patient than in the first series, as shown when Last Order commented on her panties. She simply laughed at the comment and moved on. Another example of this is her patience with Cendrillon, barging into her apartment naked after she "cooks her up", only losing her patience and destroying part of the apartment she lives with the others after she asks to make her a Cinderella dress and then comments on how Mugino was training to be a good wife. This may be, however, an example of her continued mercilessness towards her enemies, though now it has a focus, using it to defend the people she cares for, like Shiage, Fremea, and the rest of ITEM. Indeed, she surprised an assailant who dressed up as Frenda and hacked her artificial eye, believing she has mellowed out after the War. Here, she states that she will get into trouble and into fights, kill people, and even destroy things, but no matter what, it will be fine and will be resolved in a happy ending because as long as she has Shiage, it will be fine, for he will forgive her in the end.

She has the tendency to drag the pronunciation of words, specifically she uses it on people who has angered her such as "Haaamazuraaa."

Background
Not much is known about Mugino, though it is shown that when she was young, she was incredibly wealthy and even had a butler. She also seemed to have a snobbish look as a child. Shiage himself recalls that, in his time as ITEM's lackey, she always looked like a glamorous and elegant girl, who seemed as though she grew up as a rich girl.

It is likely that Takitsubo Rikou's inclusion into ITEM with Mugino Shizuri giving her Ability Body Crystal was unbeknownst to them, likely part of the research on Takitsubo and her AIM Stalker. Due to her knowledge in the inner-workings of Takitsubo and her AIM Stalker, it is likely that the ITEM liaison was the one who recruited Takitsubo into ITEM for this purpose.

Battle Royale Arc
Prior to the start of the events of October 9, she likely participated in the killing of SCHOOL's sniper, though they were unconcerned on why they targeted Oyafune Monaka in the first place. She first debuts along with all the other members of ITEM immediately after the assassination attempt on Monaka's life by SCHOOL in a family restaurant. Mugino wonders if her salmon bento is different from the day before, though Shiage silently comments on how it is the same. After Hamazura Shiage mulled on the uneven male to female ratio as well as Mugino finishing her lunch, Mugino begins saying on how before noon, someone attempted to assassinate Monaka. Mugino states that the higher-ups want to them to take action regarding that. Frenda comments on that she doesn't have information on that. Hearing this, Mugino orders Shiage to send the details of the incident to everyone's cellphone. With a halfhearted response Shiage does so, though he accidentally sends a pornographic video (likely related to bunny girls) he downloaded from the Internet. When the ITEM members see this, all of four snapped their cellphones shut and looked at him with scorn. Shiage tries to amend his mistake by trying to send the information again, but he however is chastised by them. Mugino is lost in words, only being able to say his name. Frenda says that he is disgusting. Kinuhata Saiai asks if Shiage likes bunny girls. Finally, Takitsubo says that she is rooting for him. Trembling at their words, he makes sure at sending the information to all for them.

Their conversation begins with Kinuhata Saiai pointing out on how she was sure that they took out SCHOOL's sniper three days before. Mugino says that SCHOOL likely hired a new one and ignored their "warning". Frenda Seivelun states that back then they didn't debate why they were targeting Monaka, but realizes that there must be something up if they still wanted to assassinate her despite her low value even amongst the Board of Directors. Takitsubo Rikou adds to Frenda's conclusion, repeating what Mugino says. As Mugino tries to think on the reason why SCHOOL went out of their way to try in killing Monaka again despite her low value, she asks for Shiage's opinion. Shiage tries to give an answer but his response didn't actually have anything in it. Disappointing everyone, with both Frenda and Kinuhata calling him disgusting, while Takitsubo says she'll root for him even everyone else is calling him disgusting. With this disappointment, Shiage kneels on the ground and is promptly ignored. Mugino goes back on topic and proposes that SCHOOL targeted Monaka because there's no value in killing her. Kinuhata is confused, to which Mugino says that SCHOOL probably didn't care who it was as long as it caused a disturbance, choosing a VIP whose death whose death wouldn't have much of an effect and didn't have strong security. Frenda then states that she feels sorry for Monaka. Feeling proud, Mugino gives her hypothesis on what SCHOOL is after, starting on how if a VIP of Academy City are in danger, people are called in from all sorts of places. She says that roads are blocked off in order for ambulances to travel on as well as important people from various medical industries gather at the hospital for them. Saying this, Mugino asks on what would happen if someone attempted to assassinate a VIP, and she answers on how people will be called in to protect the facility where the VIP will undergo treatment. Mugino concludes that SCHOOL will do something amidst the confusion. Kinuhata states that their methods are boring. Mugino then speculates on what the facility they would be targeting after the creating the commotion. Frenda concludes that Monaka was just SCHOOL's insurance for their plan to be in order and that they are still planning on attacking their real target, to which Mugino agrees. Shiage then speaks up again, asking if what SCHOOL did was really an attempted assassination. Mugino says it probably didn't matter as Monaka may be revived by Academy City's mysterious technology even if she died. Mugino then orders that they need to find the facilities that have insufficient security due to the assassination attempt. She then adds that they also need to see what has changed had the assassination been successful, stating that SCHOOL may have made a situation where they could move whether the sniper succeeded or not, indicating that there might be a facility that has its security reduced regardless as it may be where SCHOOL is headed. She then orders Shiage to find a car for them as they may be heading out soon. Shiage becomes irritated on how Mugino said her orders, but he is forced to acquiesce. However, Shiage complains on how he was once the leader of over 100 Skill-Out, to which Mugino says that it is true though she doesn't his point. Shiage then leaves to find a car with a heavy heart.

During BLOCK's hacking of the Virus Isolation Center the ITEM liaison tries to call Mugino Shizuri as she and ITEM prepare to leave to take on SCHOOL. Shiage points out her call, but Mugino tries to ignore it, though the liaison is quite persistent. Mugino later answers the call, much to her frustration. The liaison says that there is an emergency in the Virus Isolation Center and tells them to deal with it. Mugino is apathetic to it, prompting the liaison to complain and that the Powered Suits are currently busy in searching the body of someone called Terra of the Left. Mugino replies on how they are busy and asks if they can do this later. This prompts the woman to complain again, telling her of their purpose, and reminding her that they weren't able to protect Monaka from SCHOOL even after they said they killed their sniper. Apparently fed up, she tells her that she'll ask someone else to deal with the Virus Isolation Center and that they need to write a report on the attempted assassination. Mugino says however that they can't do that as they are about to destroy SCHOOL. Hearing this, the woman stopped complaining and asks them to shoot each member of SCHOOL at least 10 times for her. Mugino says that her reply was awkward and tells her she's supposed to try and stop them. The woman says not to worry about, stating that she hated SCHOOL for a long time, and that everything that worries her should be eliminated from the Earth. With that the woman ends the call laughing, leaving Mugino quite confused. Mugino then tells Shiage to get them a car, the girls get on the car Shiage had just stolen for them, impressing Mugino. Shiage asks where they are going, to which Mugino states that they'll be going to Kirigaoka Girls' Academy in School District 18 as there is a particle engineering laboratory nearby that she believes is SCHOOL's target as the place has become disrupted after the assassination attempt on Oyafune Monaka. Mugino mentions that there are multiple places that she suspected but states that the particle engineering laboratory. Hearing this, Shiage asks what they are after there, though Mugino says that she doesn't know, but says that it is better than dealing with the whole Oyafune Monaka thing. Shiage then starts the car. Takitsubo then asks if Shiage has a license, to which he responds by saying that he doesn't need a card to drive, only skills. He then drives ITEM with the automatic transmission car.

ITEM and SCHOOL then clash in the laboratory, with ITEM, most likely Mugino, ending up eliminating the Boy with goggles. The latter apparently not risking a battle later tries to escape in a station wagon. Not wanting to lose her quarry, Mugino Shizuri later takes Takitsubo with her (likely because she is the only one who can track SCHOOL) and leaving Kinuhata and Frenda behind. Shiage asks where Kinuhata and Frenda is, to which Mugino says their battle back in the laboratory won't be enough to kill them. As Shiage follows the station wagon, Shiage sees her sporting the marks of battle, with her face swollen and clothes burned. Shiage asks what had happened, commenting on how she's supposed to be the 4th-ranked Level 5. Mugino then says that SCHOOL had a Level 5 as well, the 2nd-ranked Kakine Teitoku. However, Mugino comments on how in spite of him, they took care of one of them. Shiage then asks what she'll do when they caught up to the station wagon, to which Mugino says that they'll defeat them and take back what they stole. Mugino then says that they stole the Tweezers, though Mugino fails to explain it to Shiage, stating that only he needs to do was to catch the station wagon. Mugino then begins doubting that they can catch SCHOOL with the car they have, to which Takitsubo says not to worry. Takitsubo says that her AIM Stalker can track down the owner of any AIM diffusion field she has recorded, as such she can search and find them even if they leave the solar system. Shiage then reassures Mugino, saying they have an excellent navigator, as such they won't get away. Suddenly, they see a mobile crane before them operated by a certain girl, intercepting the car ITEM was in. With her skills, she is able to hit the car, pushing it towards a wall. Mugino Shizuri explains to Hamazura Shiage that the ones who are attacking them are SCHOOL, wanting the station to get away. The Girl backs up the mobile crane for about 10 meters as she tries to strike the car again. Seeing this, Mugino orders Shiage to smash the windshield of the car as it had crush the doors too much. They are able to escape the car just in time as the Girl crushes it with the wrecking ball and later explodes. With the crane's engine apparently stalling, the Girl comes down to go after them personally. Mugino tells them that they should split up. Shiage asks why she couldn't stay and fight, to which she says that she is after the Tweezers in the station wagon they were chasing, and does not care for subordinates like the Girl in the dress. Furthermore, Mugino states that the Girl's power is troublesome. With that they leave in different directions.

Mugino then comes up somehow with a corpse, then calls Shiage after he escapes the Girl in the dress. She asks him that he didn't screw up, detained, and had someone put his phone up to his ear. Shiage says that he is fine and assumes that Mugino is too. Mugino commends Shiage for his efforts, saying that she had things a lot easier because of it. She then apologizes, stating that he needs him to come back as she needs him to dispose of a body.

They are in their Private Salon in School District 3, regrouping with the rest of ITEM minus Frenda. When Shiage arrives after escaping the Girl in the dress of SCHOOL, he asks where Frenda is, to which Mugino says that she is gone, dead or captured. She says that in a manner in which she is not particularly caring of her fate only inconvenienced by it as there are only three members left of ITEM that could take SCHOOL down. Mugino then becomes optimistic as they have Takitsubo for searching. Takitsubo notices Shiage is hurt, but tells her to not mind, he then asks what they are going to do now as SCHOOL has already stolen the Tweezers. Mugino asks Takitsubo if searching for Dark Matter is fine, to which Shiage asks who that is. Mugino answers that Dark Matter (Kakine Teitoku) is the one who leads SCHOOL. Takitsubo then prepares to use the Ability Body Crystal to use her power. Here, Kinuhata sympathizes with Takitsubo's handicap, as she is unable to activate her power without the use of the drug. After licking the powder of the Ability Body Crystal, Takitsubo's power begins to activate and searches for Kakine. There, she concludes that he is within the building. Before they could react, Kakine Teitoku himself appears before them, kicking down the door to their salon. Kakine tells them that he has come to declare victory, but Mugino just mock him for being the Spare Plan and running away a while ago. The two of them banter regarding the teammates SCHOOL lost thanks to ITEM. They are however interrupted by Kinuhata picking up table and smashing it on Kakine. However, his expression remains unchanged, only exclaiming that what she did hurt. Seeing this, Kinuhata runs towards a wall and destroys it with her fist. She then grabs Takitsubo and Shiage, winking towards Mugino as she leaves into the hole.

Their fight continues with Kakine coming out as the victor, though apparently believing that he has killed Mugino. Mugino later contacts Shiage, who at this point is determined to save Takitsubo and stop her from abusing Ability Body Crystal. She wants to start a counterattack against SCHOOL and use Takitsubo again to use her power to track them even if it kills her. After Mugino escaped Kakine during SCHOOL's attack on ITEM in the Private Salon, Mugino either somehow discovered that Frenda betrayed them or came to the conclusion that only Frenda could've betrayed their location herself. She goes on a solitary manhunt for Frenda, already deep in her desire for vengeance against SCHOOL. Mugino later finds and executes Frenda, cutting her in half at the waist with her Meltdowner ability.

Shiage does not follow her orders, trying to find a way to get her as far away from ITEM as she could. While carrying her, Shiage comes upon a bridge where Yomikawa Aiho comes upon them and tells Shiage that although she doesn't know the situation, she'll be taking Takitsubo with her. Seeing this as an opportunity to allow Takitsubo to escape from Mugino, hands her over to Aiho, surprising her. Shiage hastily explains that she has been using Ability Body Crystal, which is slowly killing her. At that moment, a bloodied Mugino appears before them, carrying the upper half of Frenda's corpse, whom she killed for her betrayal. Shiage pleads to Aiho to leave with Takitsubo as she has no way to take on Mugino, the 4th ranked Level 5. Aiho hesitates for a moment, but acquiesces and tells Shiage not to die, as she will bring a fully armed Anti-Skill team once she gets Takitsubo safe. With them gone, Mugino crosses the bridge and says to Shiage on how battling with one's life on the line makes on feel numb. Shiage tries to reply but Mugino tells him to quiet as she didn't ask for his opinion. She then punches hard on his gut, making Shiage nearly vomit. Mugino still hasn't given up on using Takitsubo and finding SCHOOL. Shiage laughs and asks if she should really be finishing him of that moment. She turns to him in an irritated way but is then surprised on what Shiage does next. He shows his hand holding the case for the Ability Body Crystal that is needed for Takitsubo to use her AIM Stalker ability. Mugino is enraged, but before she can do anything about it, Shiage jumps over the metal railing and off the bridge, landing, though not gracefully, on a train that had just passed by. Here, Shiage intends to lead Mugino away from Takitsubo using the Ability Body Crystal. His smile as he got away from Mugino is cut off however as the train suddenly stopped. Nearby, he saw that Mugino has stuck her hand into the ground and cut off the power cables that the trains used using her ability. From afar, Shiage could tell what Mugino was saying through her lips—she was going to kill him.

With the train stopped, Shiage hurriedly tries to shake off Mugino. He comes upon a crowd and here discovers however on how relentless Mugino could be, already sighting among the people there. Seeing as how he cannot get away from her by mixing in with a crowd, Shiage continues running and goes inside and discovers to find that he is in a deserted refinery for biological ethanol fuel with all its machinery and paraphernalia. As he wonders about the place, Mugino arrives behind him, complimenting him on finding a deserted place for him to die alone. Before he could turn around, something hits his back, making him fly a few meters before landing, knocking over containers as he does so. Despite being pain, Shiage didn't suffer any broken bones and can still move. He leaves the large area and comes upon a room with lots of machinery, allowing for blind spots and hiding places. Here, he ponders how to defeat Mugino. He knows she isn't invincible even if she is a Level 5. He cites their encounter with the Girl in the dress and the train power cables, thinking that since she didn't destroy the wrecking ball with her power, and destroyed the power cables underground instead of the train, there must be some limitations to her power. Here, he believes that Mugino's power takes a certain amount of time to aim in exchange on how powerful it is, making her weak to surprise attacks, a fundamental flaw of her power being too powerful that it could endanger even her. Then, he hears her calling out his name.

An intense sense of danger fills Shiage, and he decides to quickly go down on the ground, only to discover that immediately after the place where he stood was then covered by her beams. Small explosions occurred afterwards due to the alcohol, a few of its heated debris landing on Shiage, making him shout in pain. Since the areas for cover were in her way, Mugino was just going to destroy them all, forcing Shiage to face her. Mugino comments on how the machinery reminds her of the goldfish scooping games at festivals though she forgets the name. Nevertheless she says that they are no match for her Meltdowner. The machinery has now been reduced into rubble and even the outer wall have been damaged. Mugino stands in the center of it all. Here she states on how researchers have said that her survival instincts keep her from putting on more force than what she usually gives out but says that it was originally enough to kill the Railgun instantly, though she states that if she does so it would blow her body to pieces. Then Mugino approached Shiage.

Moving to a different floor in the plant, Shiage keeps dodging Mugino while she continues her pursuit. Mugino shouts to Shiage on how he should stop getting out of his way and give her the Ability Body Crystal and Takitsubo as she won't be satisfied until she destroys SCHOOL. Of course, Shiage rejects her as Takitsubo is in her limit. Mugino gives a callous response to this, saying that she can be replaced as long as they can find SCHOOL. Shiage persists and states on how she would be unable to defeat the 2nd-ranked Level 5 based on facing him twice and the fact that he met the man himself. Shiage asks on what good Mugino would gain in finding where Kakine is. He tells Mugino that he will not allow Takitsubo to die for something so pointless. Mugino however laughs scornfully at his remarks. She asks on how Takitsubo drew her in, noting that he might have fallen for her cute face or kind words. Mugino asks him if he thinks everyone who speaks kindly to him is a good person and everyone who talks to him harshly is a good person, stating that it makes himself look like the center of the world. Shiage doesn't deny Mugino's words, and believes that if Takitsubo wasn't nice to him he wouldn't have made his decision. However, Shiage shouts to Mugino on how Takitsubo didn't want someone like him to die simply because she was like that. He states that a person like Takitsubo needs to be happy, saying that if they don't create a society where the kind idiots like Takitsubo could stand at the top, their world would never get any better.

Mugino did not reply to this and fired off another beam towards the metal rubble where Shiage, knocking him back. Then, before Shiage could turn around, Mugino comes upon him from behind and sticks a screwdriver in his right ear. Stuck in place, Mugino held out her other hand and demanded for the case of the Ability Body Crystal. Shiage had a plan however. He gritted his teeth as he took the case from his pocket, and completely ignored the screwdriver and forcefully spun around.

This act shocks Mugino as the screwdriver carves the inside of Shiage's ears. Despite the pain Shiage's plan has been fulfilled and he sticks the case of the Ability Body Crystal into Mugino's right eye. Immediately after Mugino screams in pain as her right has been crushed, gripping the affected area of her face. Shiage smiles and taunts her. Mugino screams in rage. She tries to use her Meltdowner on Shiage, but fails to aim properly, obliterating her left arm. What was worse for her is her shot missed Shiage. Still relentless, she shoves Shiage down and climbed on top of him, making him lose his grip of the case, slipping across the ground away. Mugino however was too consumed in rage to care anymore as she stares Shiage down with her remaining eye. She mocks Shiage's words, saying that he can tear of her arms and legs and crush her organs but he can't change the difference between their strengths for he is a Level 0 and she is the Number 4, the Meltdowner. As she grabs Shiage's neck, he smiles. He says that he is no idiot and knew their confrontation would end up like what was happening now. Mugino listens as Shiage sums up her relentless and obsessive personality using video game metaphors. Mugino is someone who doesn't like messing up even slightly, and when someone like her messes up, they'll find another goal that they could accomplish absolutely. He tells Mugino that she could have picked him off at a distance instead of obsessing over a Level 0 like him. He then says that it is her ridiculous obsession with victory left a decisive opening for him. At that moment, Shiage took out the ladies' handgun that Hattori Hanzou gave him a while back as final ace in the sleeve. Shiage then empties all the bullets of her handgun on Mugino's upper body. Mugino continues to stand and looks down upon herself in shock. Then Mugino falls and stops moving, with Shiage remarking on how it was too easy. He picks back the case of the Ability Body Crystal and begins leaving with his battered body.

However, as he does so he hears Mugino muttering his name, and as fear grips him again Mugino howls loudly for his name. Despite her injuries, Mugino Shizuri stands up once again and once again tries to use her Meltdowner. With no options left, Shiage runs toward Mugino and there they clash again. Shiage punches Mugino in the face, and there Mugino is finally felled by Shiage. He then picks up the handgun he cast aside and contacts Aiho on how back-up isn't needed anymore as it is all over.

Members of the ITEM's subordinate organization waiting outside of the facility later enter it after Shiage leaves in order for them to destroy evidence. Knowing that Shiage just defeated a Level 5, they don't do anything to stop him. They most likely picked up Mugino's injured body there.

DRAGON Arc
In Volume 19, they are replaced with masses of energy with the help of her own ability and states she is alive as a result of Dark Legacy and she is way better off than #2.

World War III Arc
When she reappears in Russia, she acquires a replacement arm and a monocle that snugly fits in her right eye socket. After losing her arm every encounter that she has with Shiage will leave Mugino more and more imbalanced, developing a huge obsession with getting rid of Shiage and by extent Takitsubo. She becomes obsessed to the point of abusing Body Crystal to defeat Shiage. By the end of volume 22 she finally decides to make peace with herself and with Shiage, finally returned to being the "old Mugino" who trusted her teammates and friends.

Freshmen Arc
Mugino has had her eye replaced with a mechanical one and covers up the rest of her injuries with makeup and has gotten a prosthetic arm that she is able to use as well as a real one. These replacement body parts make it look almost exactly the same as how she used to look before she fought Shiage. She has also rekindled relations with the rest of ITEM and is shown to regret having killed Frenda.

Homecoming Arc
Sometime later, Mugino and the girls go in search of Shiage, and confront him at Kamijou Touma's apartment. Here, she has a brief encounter with Accelerator.

Eve of the Festival
Mugino stays behind in the ITEM apartment, performing various menial tasks, specifically cooking, in order to determine the readjustments needed to carry out on her prosthetic body parts. Cendrillon mails herself to their apartment, most likely intending to meet Shiage, one of the persons who opposed her and GREMLIN during the Hawaii incident. Mugino receives the package, and though she knew she did not order it, went along with the instructions. She successfully "cooks up" Cendrillon. She introduces herself to Mugino and tells her of her goals also complaining that she had not used a sufficient volume of the ingredients which led to Cendrillon appearing much smaller than before. Mugino is unperturbed by this situation. Cendrillon then asks Mugino to make her Cinderalla dress, at which point she has exhausted Mugino's patience after she states that whatever Mugino is doing looks like good training for a wife, who proceeds to attack her with her Particle-Function Waveform High Speed Cannon, destroying a part of the apartment she and the rest of ITEM are staying in. Cendrillon escapes with only a towel and the instructions for sewing her dress on her person.

She and Kinuhata later clean up the apartment, where she tells her on how she made a person using ingredients, much to her confusion. Later, she leaves the apartment after seeing that they need water bottles. After Kakine Teitoku is released by Kihara Yuiitsu to go mad in the City, a being that sounds and looks like Frenda appears before Mugino after she goes out to get some water bottles. Here, the Frenda-being tells a clearly-shocked Mugino that she is different from the last time she saw her, and that despite her coming to terms with her death, it doesn't mean that her anger should disappear. It was half an hour before midnight, and Mugino faces off a being that looks like Frenda. Seeing the shock, the girl comments on how it not impossible for a city such as Academy City to contain oddities such as herself. The girl asks why Mugino took for granted how she would feel about what happened, and then asks if she is going to kill her again, to which she concludes that she could not and taunts her for it. The girl tries to attack Frenda, but is felled by Mugino, who did not hesitated on blowing away the girl's right arm.

Mugino frowns upon the person who pretended to be Frenda, stating that her artificial eye have been interfered electromagnetically, which made her see things that shouldn't be there. She also assumes that the person is also using a voice changer since she couldn't tell the difference. Kinuhata then comes up after noticing the commotion, and firmly proves Mugino's suspicions, it was a middle-aged man dressed in Frenda's clothing.

Mugino insults the man's foolishness, telling him that he could've have comrades to jump at her when she was fooled. The man writhes in pain, asking on how Mugino could still fight despite living a peaceful life away from the dark side. Mugino sighs at his explanation. She states that she will get into trouble and into fights, kill people, and even destroy things, but no matter what, it will be fine and will be resolved in a happy ending, because as long as she has Shiage, it will be fine, for he will forgive her in the end. She states, that she too is an oddity, and there is an oddity in Academy City that would allow her to live despite what had happened to her body. At which point, she mutilates the man utterly into a broken ruin, but keeps him alive as an example to what she had said. She and Kinuhata later dragged his ruin before a strange research facility, and tells each other to keep a secret from Shiage.

During the Festival
After Shiage, Takitsubo, and Yoshikawa Kikyou escape the Dark Matter beetles released by the revived Kakine Teitoku through the help of Beetle 05 at the expense of Fremea and Last Order following it, Mugino and Kinuhata appears before them. Kinuhata explains how they got here, to which Shiage explains to them the situation in "30 seconds." Mugino was polite in the beginning but became displeased as Shiage's story went on, and had grabbed Shiage by the collar. She is angry towards Shiage for having no idea where Fremea is, and allowing her to leave with a probably dangerous out-of-control weapon (Beetle 05), and the fact that he has no idea why she was being attack or who was behind all of it. Takitsubo and Kinuhata frantically try to stop Mugino from making Shiage worse off in her anger, but later tosses Shiage aside near a tree. Mugino tells that him believing that he will be defeated once he is spotted from whether he's 4 kilometers or 1mm away, as well as his plan on opposing the beetles as nonsensical. She is further enraged after he asks where they could find a means of attacking from kilometers away that can break through the beetles' armor. She tells that they all need firepower that can take out the likes of those beetles 5 kilometers away, and states that it is easier than spinning a pen in her fingers. Shiage still doesn't understand, to which Mugino asks if he thinks the 4th Level 5 is cheaper and harder to use than a rocket launcher, as Mugino continues to step on Shiage as punishment.

Mugino then asks Shiage, and asks what had happened to the security buzzer that Shiage gave to Fremea. Shiage's actions seem to indicate he forgot, and as Mugino prepares to deal out punishment, he takes out the GPS tracker to find the security buzzer, ending up next to the multi-level overpass. There, they find Fräulein Kreutune, and was about to witness the battles that was about to occur for her sake. Then, Cendrillon comes up to them, who rudely tells Mugino to point her to their apartment again, angering her. Cendrillon ignored their reactions and tells them that she has left some of her ingredients in back in the apartment, and that she needs them in order to resolve a large problem in the city. Mugino is annoyed and not wanting to deal with the situation took Shiage and told Cendrillon that he will show him the way to the apartment. Then, with all this commotion, Yoshikawa Kikyou tells them that the girls are together and are with a large rhinoceros beetle, though she says that they are safe for the moment. Mugino, unused to having information being given without compensation in return, is surprised with Kikyou's actions, which she points out. She tells them that Kakine Teitoku is trying to kill them, and asks for their help. Mugino says she doesn't care as long as she gets Fremea away from Last Order, but Kikyou notes on what Fremea would feel if that were to happen.

Shiage tries to diffuse the situation, saying that if Fremea's friend is about to be killed, there's nothing wrong with fighting to save her. With that, despite in her displeasure, concedes, and asks where Kakine is, to which Kikyou states that they are in the underground passageways of the multi-level overpass, noting on the behavior of Level 5s fighting. She also states that she also has to deal with Last Order being eaten. Cendrillon then speaks up on how she will be needed to keep the girl from being eaten, surprising Mugino. Cendrillon states that to protect Fremea's friend, they also must protect Fräulein, as is the will of Kamijou Touma. After Mugino translated her words, Shiage recalls the softhearted mood that pulled others together in Hawaii after hearing Touma's name. Shiage says to Takitsubo on how he is completely annoyed with the situation, but cannot overlook it. They then ask Cendrillon on how they could stop Fräulein Kreutune, to which Cendrillon says that Fräulein Kreutune will eat a specific person's brain, and that she left the materials needed to use against her back in the apartment. With that, they all went their separate ways in order to protect Fremea's friends, with Mugino going to the multilevel overpass.

Mugino appears in the lowest level of the multi-level overpass, saving Accelerator from the reformed Kakine Teitoku after he was overwhelmed by him through his usage of Dark Matter Misaka clones. It kills one of the clones that Kakine made from the memories of the area using his Dark Matter. She berates Accelerator for his actions, enraging him. She tells him that he is being angry at the wrong person, and references Kakine's words on how "Only the one who was killed can understand the feelings of the one who was killed," is correct but states that the clones Kakine made in here isn't really them. She continues that it is not the likes of them, people who have killed others, to even begin understand what the dead feels as it is not their purpose. She states that Accelerator is incredibly naive to fall for a Kakine's tricks, and asks if he thought that they might come back to life and that his crimes for killing them would be undone. She says that she has read about the clones, and that his reasons for killing them was not worse than her killing others for no reason. She tells him that they are both going to hell, but there are things he needs to do before he goes. She asks what he will do, telling him that she doesn't care if he allows himself to get killed, or retrieve the dead's dignity and peaceful rest from the one who desecrated their graves before him, it is his choice.

Accelerator acknowledges this, regardless however, the clones before him is the final proof that those he killed ever existed. Mugino replies that it is all the more reason, and him finding it acceptable for someone to steal and control the dead, then he should just let himself be killed as she will take care of everything. She then feels uneasy and tells Accelerator that he has to dirty his hands to give the dead a clean end. She references what Kakine said again, and says that only the living can act based on their feelings for the dead, and rejecting that and running away is neither being honest or pacifistic, but plain cowardice. And with that, Accelerator is released from his stupor and tells her that he will destroy, that he will be the remnant to prove that those people he killed really existed.

Kakine finally reacts after listening to them, and asks if they will stop thinking how the dead feel and stop thinking about it. Mugino tells him that he will never understand, for he is someone who puts words in the dead's mouth for his own benefit and runs away from his feelings regarding the dead himself. She tells him that he is pathetic even though he is powerful, and would've been better if had remained dead for he would've been merely the esper that defeated her. Then, she tells him the reason she was in there with them. On how someone who pretended to be Frenda attacked her last night, and suspects him for it for he was the biggest factor from the dark side of Academy City active at that time and the interest in playing with the dead was the same. She tells him that she doesn't know what his purpose was with what he did, and tells him that she will make him pay for disturbing her grave.

And with that, their battle begins. Mugino used her beam on Accelerator for his use, redirecting it to all the false clones Kakine created at once, destroying them. Accelerator directs his attention towards Kakine, and uses his vector powers to destroy all the Dark Matter spears he created. As he twitched, Mugino fired at him, obliterating the top half of his body and most of his legs. However, Kakine appears upon a wall, saying that he can recreate himself. Mugino asks if he moved his flesh and blood organs into the floor before her attack. Kakine redirects the question, and hints many possibilities now that he can replace and create practically anything with his power.

Accelerator does not care however, ripping apart the countless spears and redirected the signals in the center point in the puddle, but to no avail, as Kakine states the network of his Dark Matter expands and information sent faster without direct wiring than he can destroy it. Despite this, Accelerator continues to try and destroy his Dark Matter, as Mugino continued to assist him, Kakine then asks how much battery time Accelerator has left, and is curious about the wings that no theory can explain. Kakine just brags on how time is running out, and that he has no problem taking down Mugino. They continued attacking destroying his head, but it is of no avail, as he tells them that he simply has an infinite supply of Dark Matter, and his inspiration is boundless, telling them that to reach him, they need to climb over the wall of infinity that continues on eternally. He then shoots out countless Dark Matter spears towards them.

Kakine continues his assault, but time is running out, and Kakine simply taunts them as his Dark Matter attacks continue to shoot out. But then, something happened; he stopped. Mugino becomes curious, threatening to kill him. But Kakine does not answer, as he too is confused. He then asks what Accelerator did, believing him to be the culprit. Then, Accelerator realizes something. He tells Kakine that this was the effect of him being "infinite," and tells Kakine that it wasn't him.

He did not know, but Beetle 05, the rogue beetle that Kakine ignored, was beginning to take over. As the system begins to transfer authority to Beetle 05, Kakine begins to crack, who cries on how it is not possible for a power that he brought betray him. Accelerator then tells Kakine that it is no longer matters who was the first Kakine, as he obtained in infinite. Mugino too began to understand. She laughs at his problem of being too powerful, saying that when a network made up of flexibly replaceable equipment has a portion become isolated from the rest, the isolated portion becomes a small network of its own. Accelerator concludes that the one who stopped Kakine Teitoku was now the Kakine Teitoku. Accelerator is impressed on Dark Matter's capabilities, and mocks him for being unable to wield it. Mugino however notes that he might not be the core Kakine as he had scattered his mind over the system, and the one before them was closest to the surface, though it says of nothing that what showed itself in the surface was the true nature of Kakine Teitoku. Mugino then asks if they were just battling the outer layer of his mind, and tells that it wasn't easy doing it. Here, she is impressed by Kakine Teitoku, being not a normal person, but not the one before her right now.

Slowly, despair overtakes Kakine and slowly more cracks form. Accelerator comments on how there will probably nothing left to prove that he was here, and even if a massive amount of data is left concerning Kakine Teitoku, it will not refer to him. In the end Kakine realized the reason for how this came to be, and he shouts his fury in that underground passageway with only Accelerator and Mugino as his audience. Accelerator however, had enough, and pierced his center of the thing before them, completely shattering it, and the Dark Matter dissolved into the air, leaving nothing behind.

Accelerator comments that it is over, but Mugino just shrugs, saying that they still have a long way to go for people like them. While leaving the underground passageways, Mugino asks if he intends to do anything about Fräulein Kreutune, to which Accelerator replies that he doesn't care, but is intrigued by the fact that someone he knows wants to protect her and risked herself to stop him from killing her. As they got out into the open, Mugino sees Fräulein eating something which she presumes to be a human brain, and witnesses Accelerator's near rampage as he produces wings after he presumes it was Last Order she was eating.

Agitate Halation Arc
Mugino arrives at Learning Core alongside Kinuhata Saiai and Takitsubo Rikou, presumably drawn to it as one of the "heroes" affected by the Agitate Halation Project. She is dismayed by Shiage not giving them enough information for them to find Fremea, and later quickly shuts up Fusou Ayame with her Meltdowner along with other several people. She may have also witnessed Sogiita Gunha blowing Ayame and several other people as well before Mugino could attack her in earnest.

Magic God Othinus Arc
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, all of ITEM are alive and well. They are first seen after Touma's heart has finally broken and has decided to kill himself in order to preserve the broken world. Here, they are in a family restaurant, with Frenda arguing with Mugino regarding her preference with the salmon bento, forcing Mugino to fire back with a criticism regarding Frenda's preference for canned foods. Kinuhata comments on how both of them are focused on seafood and that they should make their characters more distinct. Takitsubo then comments on how they get along surprisingly well. Then Hamazura Shiage, Hattori Hanzou, Komaba Ritoku, and Fremea Seivelun comes along into the restaurant. They are late as Hanzou took them to a shortcut. Kinuhata asks why they are late and why their efficiency is dropping as they gained more subordinates. Shiage blames Hanzou for the shortcut they took, but Hanzou says it is because Ritoku could not leave a vending machine with a roulette alone. Frenda wonders how Fremea could be so attached to a macho man like him.

Later, as one of the seven Level 5s of Academy City, she is one of the recipients of the email giving an order to kill both magic god Othinus and Kamijou Touma. Here, she is annoyed by the fact that Denmark is too far away and that even if she did kill them, if the city doesn't pay travel expenses, she would barely break even. She doesn't follow the kill order however.

St. Germain Arc
The girls of ITEM are in Dianoid's mid-level waiting for Shiage as he is still working with Stephanie Gorgeouspalace. Mugino and Kinuhata later get into an argument on what to do to pass the time, while Takitsubo is ignored.

After St. Germain has sealed the Dianoid, Kinuhata checks the exits and finds that they have been fused. Kinuhata wonders if it is because celebrities use the top level of the Dianoid as vaults, to which the conversation moves to them discussing about Frenda's own hideout in the Dianoid. As Shiage isn't with them, Mugino decides to create an escape route using her Meltdowner. Despite firing several times on Dianoid's walls, it simply regenerates. Takitsubo and Kinuhata chastises her for continuously repeating her actions. Takitsubo then asks what they should do next leading to Mugino to once again continue trying to use her Meltdowner on the Dianoid, much to Kinuhata's chagrin.

After St. Germain notices Mugino's incessant attacking of Dianoid, one of them confronts ITEM himself. As he rambles on about his plans, Mugino orders Kinuhata to protect Takitsubo. Mugino is annoyed by St. Germain's overconfidence, and later vaporizes his arm and the Chambord spear it was holding with her Meltdowner. As people panic at their battle, St. Germain still projects an air confidence despite his missing arm and then later makes a suicide attack on them using a bomb strapped on himself. Despite this, Kinuhata saves him by tearing the bomb off him and the throwing it away.

As Stephanie Gorgeouspalace is running away from the countless Chambord spears used by the St. Germains, she is later saved by Mugino Shizuri, noting to her that the suicide bomber is still alive. Here, it is shown that ITEM has figured out the people who call themselves St. Germain are somehow being "controlled". Takitsubo then tells Mugino to fire a Meltdowner beam toward an atrium, apparently noticing that Shiage was nearby and show to him that they are still alive. They are then attacked by the spears again, but this time they are forced to contend with actually not killing any of them.

ITEM continue their battle with St. Germain, with Kinuhata using her Offense Armor, while Mugino used her prosthetic eye to track the spears then crush them with her prosthetic hand. As they battled they noted how weak an individual St. Germain and wonders if they are trying to buy some time instead of winning. As they wore them down, the St. Germains fall back. Takitsubo later discovers the reason why they fell back through one of Dianoid's monitors: they are going to use the graviton-style base isolation structure as a black hole bomb. Seeing this is as an obvious challenge, ITEM decides to stop them.

Using Mugino's Meltdowner, ITEM is able to enter the lowest level, where the graviton-style base isolation structure is located. The conversation shifts to Frenda's personality, on how she can easily spill blood but at the same time wash her hands of it and live like a regular girl. Takitsubo asks what they should do, to which Mugino says they will deal with whatever is happening and go back home. ITEM then joins Touma, Shiage, Index, Othinus, Stephanie, and Kanou Shinka in their confrontation against St. Germain.

As the battle begins and St. Germain uses the Chambord spears on them, Mugino attacks, nearly hitting Shinka in the process. Shiage calls out Mugino on this. She justifies it as she still believes that Shinka is on the enemy's side. Shiage notes that Mugino caused the mess in the first place, referring to her killing Frenda, the person Shinka cared for and the reason that led him into the grasp of St. Germain. Mugino just sighs and just attacks St. Germain instead. Takitsubo also arrives with Stephanie and her PDW as she tries protecting Index. With their sides sorted, Shinka declares that he will take back every last piece of Frenda's pride that St. Germain has perverted.

Processor Suit Arc
On December 11th, she responded to Shiage's call to meet up with the rest of ITEM after he had been sealed in the Processor Suit and was being pursued while looking after the baby Lilith, though she wasn't aware of the circumstances. She and the others were at District 7's Southern Station for the 7pm rendezvous, but failed to recognize Shiage due to the full-body Processor Suit and ended up attacking him due to some poor words from Lilith. Later, after the situation was properly explained to her, she stood guard at Heaven Canceller's Hospital to protect the feverish Lilith from further danger.

Coronzon Arc
Following the evacuation of Academy City on December 12th, Mugino and Kinuhata briefly passed the former site of the Church of Orsola while thinking of where to spend the night.

Kamijou Arc
As Academy City was recovering, having remained in the vicinity throughout the shutdown, Mugino and Kinuhata reunited with Hamazura and Takitsubo after they returned from the United Kingdom.

Operation Handcuffs Arc
By the time Hamazura returned to their apartment, as the first phase of Operation Handcuffs was underway, she and Kinuhata had already escaped, leaving behind a note. Later that day, after Operation Handcuffs was over, she leaned back against a graffiti-covered wall, spied out at the pursuers leaving without noticing her, and extinguished the light in her hand.

Level Upper Arc
She first appears during the Level Upper Arc, here, she is seen arguing with the rest of her team regarding going into public swimming pools, and is against the idea. When Frenda asks if they can go to a private swimming pool, she tells her that they can go when they have the time, much to Frenda's delight. They're conversation is later interrupted by the sound of the Level Upper treatment program being played all over the city, wondering what the sound is about.

The anime adaptation completely cuts out their conversation during this scene. It is instead replaced by a four second appearance in a cafe.

Sisters Arc
Prior to the events of the novel, she and her group are hired to stop Misaka Mikoto from destroying the facilities that are running experiments with the Misaka clones and Accelerator. During Mikoto's attack, they pinpoint two likely targets for the sabotage, here, she shows her intelligence as a leader by sending out Kinuhata Saiai to the inside of the facility to see if the attack is an inside job, and is later somewhat correct in her assumption as Nunotaba Shinobu is later caught by Kinuhata, and has Frenda guard it.

Both she and Takitsubo Rikou go to the other facility. When they figure out that Mikoto is attacking the facility Frenda is guarding, she and Takitsubo quickly bail her out, after being defeated by Mikoto, showing her immense destructive power to Mikoto in the process, forcing her to go on a defensive. With that, Mugino has Takitsubo use Body Crystal to track Mikoto during her defensive.

Mugino would later figure out that Mikoto is the one attacking the facility, and has Frenda and Takitsubo retreat, wanting to prove that she is the superior Level 5 herself. In their battle, she shows her superior physical condition to Mikoto, as the latter has been attacking facilities for several days without rest, forcing Mikoto to use Frenda's traps she left all over the facility as an advantage, making Mugino enraged at Frenda for carelessly leaving her traps. Mugino underestimates Mikoto's control on the traps and is later knocked-out by it. Mugino later comes to, after Mikoto has finished destroying the facility and is about to retreat; even though she is nearly exhausted, Mikoto lures Mugino into a platform with Frenda's traps once again, destroying it and making Mugino fall. Mikoto tries to save her but Mugino rejects her offer and instead falls, though she breaks her fall by using her Meltdowner.

Interested on the reason why Mikoto is fighting so hard, she apprehends one of the researchers retreating in the facility and finds out about the Level 6 Shift Program and decided to let her be, deciding that it would be best to let Mikoto suffer in the dark side of Academy City.

Silent Party Arc
In the anime original arc, they are hired by STUDY under false pretenses, being used as test subjects for their Powered Suits controlled by Diffusion Ghost. For that they desire vengeance for their reputation in the dark side of Academy City. The ITEM liaison gives them information on one of STUDY's factories, destroying several Powered Suits there.

They are later present during the Silent Party, taking down several Powered Suits in a stadium, and inadvertently aiding Misaka Mikoto. Mugino briefly reappears on September 2nd, while relaxing in ITEM’s private swimming pool together with the other core members of the organization.

Daihasei Festival Arc (Railgun)
Mugino, at a reserved pool area with her team, is phoned by an informant concerning the Daihaseisai to show off her powers. But she refuses due to her current occupation. When Frenda asks to go in her place, Mugino fiercely bashes her head, comically, onto a table reminding her that she is part of the dark side of Academy City as much as the rest of her team and cannot go public.

Toaru Majutsu no Index (PSP game)
Mugino Shizuri is a playable character in the game, unlockable after clearing Accelerator's route in the game. She has her own story route, which is noticeably darker than the other routes. Here, she joins forces with Kihara Amata, who provides her a hijacked Misaka clone as a partner, and to partake in the Zero Dimensional Pole Experiment. Here, they first beat Tsuchimikado Motoharu and Kamijou Touma, earning the hatred of Itsuwa and Index, which in turn, earns the hatred of Kanzaki Kaori and Stiyl Magnus, then, much to their surprise, a challenge from Acqua of the Back. She and the Misaka clone later has confrontation with Misaka Mikoto and Shirai Kuroko, the former angered by the forced manipulation of the clone. Later, Mugino fights against Accelerator and Last Order, the latter, too, is shocked and horrified by the Misaka clone being partners with her. Finally, betrayed by Amata who plans to use her power for his experiment and activates Fuse Kazakiri to subdue her. Her basic square attacks are particle beams, which grow in width if the button is held for longer. Moreover, she can create a shield to protect herself using her the triangle button, or allow her to throw silicon cards in the stage. Silicon cards, if hit by one of her beams, spread the beam out, allowing to increase the breadth of Mugino's range. Moreover, using the Silicon Card and a single beam attack, is the only method for her to catapult the opponent in the air allowing for a Unison Raid if she has a partner. Her Overdrive is a single powerful Meltdowner beam, and her finishing move consists of her firing all four beams one after the other, catapulting her opponent into the air, and then firing a powerful particle beam at them.

Mugino is the definite long range character, though her attacks are actually more powerful at close range. She is a danger to all short range characters, like Touma, and her attacks can be thoroughly abused to not allow any opponent to close the gap. As the distance shrinks however, her attacks deal more hits overall. Mugino is vulnerable to other long range characters and attacks, as well as Shirai Kuroko, due to her teleportation ability.

Meltdowner
Mugino's ability is the Meltdowner (原子崩し (メルトダウナー) ) with the technical classification as Particle Waveform High-Speed Cannon (粒機波形高速砲). As electrons have the properties of both particles and waves, Mugino's ability allows her to forcibly control electrons in the "ambiguous" state of an electron where it is both particle and wave, and when they strike other objects the electrons are unable to react either as particle or a wave because of their state. Normally, electrons have a mass close to zero, but because they are stuck or "stopped" at this state they take the form of a seemingly solid object, which has become a pseudo-"wall" due to the "stopped" state, and then creating a highly destructive beam of high-speed electrons that pierces through a target at the same velocity that it was fired. As it is a form of electron manipulation, the ability allows her to affect electric attacks, allowing her to bend their trajectory, such as those done by Misaka Mikoto. Likewise, Mikoto can bend Meltdowner using her ability as well.

The ability usually takes on the form of a high-speed beam of light that can easily melt through thick metal walls and cause things like refined alcohol to explode with its heat alone. Mugino can create four beams at once, create a shield out of it that can disintegrate objects upon contact and block shockwaves. By December of the story's first year, Mugino can now create and use up to twenty beams at once.

Moreover, another radical application of this are limbs, like her Meltdowner arm. Also, by emitting a power similar to a rocket, it can perform high-speed evasion that is fast enough to escape an explosion.

The color of her Meltdowner differ between mediums. In the novel it described as white and pale bluish. In the video game it is of a light purple color, and in the anime it is green in color.

Weaknesses and compensations
Due to the sheer extent of her power, Mugino needs a certain amount of time to aim in exchange, as such she can't deal with a surprise attack. This weakness is demonstrated when her anger towards Hamazura Shiage fueled her to use too much power and she blew off her own left arm from wrist to elbow.

Another weakness of her ability is that despite being able to make twenty beams, she can only fire in one direction, the direction she is facing. Also, her ability can only be used on one target at a time, though it has an accuracy high enough to blow away the members of the opponent before he can draw a gun and fire. By its nature, it is incapable of rapid-fire, thus poor at surface occupation and saturation attacks. To compensate for the former, she has to consciously limit herself when using her ability and to compensate for the latter, she carries around silicon cards that can disperse her individual laser shots into multiple ones, this attack is labeled by Mugino as Silicon Burn (拡散支援半導体 (シリコンバーン) ).

According to researchers, her output is suppressed due being restrained by her survival instinct, but if it wasn't for that it could easily instant-kill the likes of the Railgun. However, because actually firing at such output would also blow away Mugino's body with the backlash, this assessment is not covered. Mugino herself understands that killing the 'Railgun in one hit' is just a poor excuse by the researchers and, for that reason, also harbors great hostility towards the Railgun.

Other abilities
Mugino is also very resilient, able to stand back up even after an entire magazine being emptied into her and having her left arm blown off. Moreover, she can give both powerful punches and kicks, as experienced by both Shiage and Mikoto, both of whom had an urge to vomit after being hit in the stomach.

After she lost her arm and eye, Mugino was given prosthetic ones. The eye allows her to track movements, while her arm is strong enough to crush even Chambord spears.

Design Evolution
Mugino Shizuri's preliminary design had her wear different clothes, and was designed by Haimura to look like a model. It is not until the design of the other members of ITEM are drawn that her current design was finalized. In volume 19 up to the end of volume 22, Mugino Shizuri receives a dramatic change of design, to which Haimura states that she is something like a horror character that chases around the main character.

Haimura gives Mugino in the 5th Shinyaku Toaru Majutsu no Index light novel, her autumn and winter attire, consisting a jacket over a shirt, and with pants and boots. According to Haimura, the reason he gave her pants was because of an illustration from the 1st Shinyaku Toaru Majutsu no Index light novel depicting her meeting with Last Order showing a pantyshot, despite wearing stockings.

Trivia

 * Mugino's animated and voiced debut was in Toaru Majutsu no Index (PSP game) in 2011, two years before her appearance in Toaru Kagaku no Railgun S.
 * Mugino's English voice actress, Lydia Mackay, also voices Kamijou Shiina.

Quotes

 * (To Mikoto, from Railgun Chapter 30) "Don't mess around with ITEM, you damned brat!"
 * (To Shiage after "purging" Frenda, from Index Volume 15): "That’s right. It seems she was afraid of SCHOOL so she betrayed ITEM and then hid. So I had to do a little purging. …What are you doing? You don’t need any purging, do you?"
 * (To Shiage, ibid): "A battle with your life on the line. A numbing feeling, isn’t it, Hamazura?"
 * (To Shiage after gouging her right eye and had her left arm explode, ibid): "That has nothing to do with this!! That has nothing to fucking do with thiiiiiisssss!! An ear!? An eye!? You can tear off my arms and legs and crush my organs, but you can’t change the difference between our strengths! I’m a Level 5! I’m #4! I’m Meltdowner! Don’t get so pleased with yourself, you motherfucker! I can kill a Level 0 like you 100 times without moving a fingeeeerrrrr!!"
 * (To Shiage after killing his pursuers, from Index Volume 19): "Don’t let pitiful bastards like that take your life. The one who’s going to rip you to pieces is me!!"
 * (Frrom Volume 19 and 22): "Why, did I become such a monster?"―It should be noted that in volume 19 she joked about it with this question, but in volume 22 she was actually troubled over this.
 * (Said to Shiage, from Index Volume 22): "I killed Frenda. And made ITEM into a mess. Plus, more than once, I tried to take Takitsubou’s life. For someone like that, how do you plan to save me..."
 * (To an unnamed assassin, from NT6): "I’ll get into trouble and into fights. There will even be deadly fights. But it will all work out in the end. No matter how many people I kill and how much I destroy, everything will be resolved in the end somehow and we can all be happy. All my past experiences have shown that to be true... That’s how it was during the fight between Item and School. That’s how it was when we fought underground in District 23. That’s how it was when we met during the fierce fighting of World War 3. And so I know it will be fine as long as I have Hamazura. No matter what happens, he will forgive me in the end."
 * (To Accelerator, from NT6): “There may be people out there who can truly imagine how the dead feel and shed tears based on it. There may be people who find something the dead left behind and finish it in their place. There may be people who save the dead in that way, but that is not something people like us who killed others while soaked in evil can do. There is nothing we can do,”
 * (To Accelerator, ibid): "You have to dirty your hands to give the dead a clean end. Only the one killed can know how the one killed feels, but only the living can act based on their feelings for the dead. …Rejecting that and running away is not being honest or being a pacifist. It is being a coward."
 * (To Kakine, ibid): "You would never understand. You are the type who puts words in the dead’s mouth for your own benefit and never faces how you feel about the dead yourself. They say not even death can cure an idiot. Well, it looks like nothing can cure you of being pathetic. You’re powerful, but you’re pathetic. It might have been better for you if you had just died back then. That way you could have ended life as the high level esper that defeated me, the #4. But you didn’t know to quit when you were ahead, and now you’re going to lose even that."
 * (To Accelerator, ibid): "We still have a long way to go. The path ahead is especially long for those of us who have killed."

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