Kinuhata Saiai

Kinuhata Saiai (絹旗 最愛) is a character introduced in the Toaru Majutsu no Index series and a recurring character in Toaru Kagaku no Railgun. She is a Level 4 esper and is an operative of ITEM, an organization in the Dark Side of Academy City led by Mugino Shizuri, and is a capable combatant in the team. As a character she has an important supporting role in the development of Hamazura Shiage as a protagonist and is one of his closest allies.

Etymology
Saiai's first name can be translated as "beloved", while her surname Kinuhata means "silk flag".

Appearance
Saiai is a young girl of 12 with short brown hair in a bobcut. . In Toaru Majutsu no Index she wears a fluffy knit dress, a sweater dress to be exact. She wears no legwear other than stripped socks, exposing her thighs and legs. According to Hamazura Shiage's assumption, Saiai may have calculated that the length of her sweater would expose enough of her thighs and legs but not to the point that her butt and panties will be exposed even if she were to bend over. Saiai later references the phenomenon while bending over, giving credence to Shiage's assumption.

In Toaru Kagaku no Railgun she is seen more modestly, wearing an orange hoodie and hot pants.

Personality
Despite being a powerful esper, Saiai is one of the most mellowed-out characters in ITEM; she isn't a screw-up like Frenda, nor is she as frightful as her leader, Shizuri. She enjoys C and B movies and likes to tease others, Shiage in particular because of his reaction to anything sexually suggestive. She is also described as being very eccentric. Despite this, she is still quite serious and dangerous during a mission, having a much more subdued mien than Shizuri or Frenda, ITEM's other combatants. She is also described as obedient-looking, a contrast to her playful personality when out of missions.

She also likes to add "super" (超, chou) to her remarks. The Funimation subtitles translate chou as "ultra". It is likely due to her brain being inserted with Accelerator's thought patterns, who has a penchant in swearing, during the Dark May Project that this verbal tic may have arose, replacing an expletive with the word "super". This is somewhat backed up by the experiment modifying the subject's personality when inserting Accelerator's thought patterns. Moreover, it is backed up by Accelerator himself who noticed his manner of speaking with Kuroyoru Umidori, another subject in thought pattern modification in the Dark May Project.

Background
According to Kakine Teitoku's speculations, Saiai may have been originally an atmospheric control-type esper when she became part of the Dark May Project, along with Kuroyoru Umidori. It was an inhuman project where espers have their minds altered after forcibly inserting a portion of Accelerator's thought patterns into them, allowing them to gain a rapid increase in the strength of their powers, though at the cost of the stability of their personalities. Here, Saiai received an idealized version of Accelerator's Redirection while Umidori received Vector Transformation, thus giving her Offense Armor. Apparentlly, she was a top esper in the project. The project was later bankrupted after Umidori killed the researchers there, explained by her to be because of her power "overflowing". It is unknown if Saiai left before or after the bankruptcy of project.

By the way Saiai was thankful for not ending up in Produce, it can be inferred that Saiai may have been a Child Error as the Dark May Project is known for using them. It is still unconfirmed if Saiai is a Child Error.

Battle Royale Arc
Prior to the start of the events of October 9, she 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. Saiai reviews several pamphlets of C-movies while they are in the family restaurant. She asks what Rikou thinks of a movie from the Hong Long Red Dragon Film Company, as she is excited for it, though Rikou only absent-mindedly replies that there is a signal coming from the south-southwest. After Hamazura Shiage mulled on the uneven male to female ratio as well as Shizuri finishing her lunch, Shizuri begins saying on how before noon, someone attempted to assassinate Monaka. Shizuri 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, Shizuri 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. Shizuri 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, Rikou 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 Shizuri 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 Shizuri says. As Shizuri 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 Saiai calling him disgusting, while Rikou 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. Shizuri goes back on topic and proposes that SCHOOL targeted Monaka because there's no value in killing her. Saiai is confused, to which Shizuri 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, Shizuri 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, Shizuri 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. Shizuri concludes that SCHOOL will do something amidst the confusion. Saiai states that their methods are boring. Shizuri 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 Shizuri agrees. Shiage then speaks up again, asking if what SCHOOL did was really an attempted assassination. Shizuri says it probably didn't matter as Monaka may be revived by Academy City's mysterious technology even if she died. Shizuri then orders that they need to find the facilities that have insufficient security due to the assassination attempt. She then adds taht 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 Shizuri 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 Shizuri says that it is true though she doesn't his point. Shiage then leaves to find a car with a heavy heart.

After Shizuri's argument with the ITEM liaison regarding their next job, to which she later approves after seeing that they are after SCHOOL, the girls get on the car Shiage had just stolen for them, impressing Shizuri. Shiage asks where they are going, to which Shizuri 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. Shizuri 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 Shizuri 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. Rikou 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.

Shizuri chose wisely as they later find SCHOOL and its leader Kakine Teitoku there, resulting in a battle. Despite the Boy with goggles being killed in the skirmish SCHOOL still retrieves the Tweezers from the facility, their goal for infiltrating the facility in the first place, and later decides to flee instead of continuing the battle. In the haste of trying to chase after SCHOOL, Kinuhata Saiai and Frenda are left behind in the facility.

She later manages to return to ITEM's 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 Shizuri 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. Shizuri then becomes optimistic as they have Rikou for searching. Rikou 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. Shizuri asks Rikou if searching for Dark Matter is fine, to which Shiage asks who that is. Shizuri answers that Dark Matter (Kakine Teitoku) is the one who leads SCHOOL. Rikou then prepares to use the Ability Body Crystal to use her power. Here, Saiai sympathizes with Rikou'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, Rikou's power begins to activate and searches for Teitoku. 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. Teitoku tells them that he has come to declare victory, but Shizuri 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 Saiai picking up table and smashing it on Teitoku. However, his expression remains unchanged, only exclaiming that what she did hurt. Seeing this, Saiai runs towards a wall and destroys it with her fist. She then grabs Rikou and Shiage, winking towards Shizuri as she leaves into the hole.

She then knocks out every other people she comes into contact with, not taking her chances if they are subordinate members of SCHOOL or not. Saiai then asks Shiage to get a car for them. She tells Shiage that one of the reasons SCHOOL is there is for Rikou, since they know where their hideout was it is also likely that the know all of their other information, and it is likely that they have discovered that they can be searched out through the use of Rikou's power. Saiai states that if Rikou is killed, ITEM will be restricted as she determines if they are the chasers or the one being chased. She continues by saying that as long as Rikou is fine they can still turn the tables around. She urges him to get a car and go into a hiding place where it isn't an ITEM's hideout. She then gives Rikou a stun gun, saying that she needs a weapon as she's always staring off into space. Just then there is an explosion due to Shizuri and Teitoku's clash, to which Saiai goes after telling them to hurry.

She is in the lobby of the indoor leisure facility, easily defeating men from SCHOOL's subordinate organization. Suddenly, she gets hit by sniper bullets, knocking down her small body despite being penetrated by them due to her power. Figuring out that the sniper was using a magnetic sniper rifle and then analyzing the bullets to determine the sniper's distance from her, she then takes out Handheld anti-tank missile warheads to attack his approximate location, destroying part of the building and ending the sniper's attack.

Then immediately afterwards, Teitoku arrives believing the sniper, Sunazara Chimitsu, to have been killed. Teitoku then recognizes Saiai as a remnant of Dark May Project and mocks her for it. Saiai however, says that she is thankful that she at least didn't get sent to Produce where the subject's brains were chopped up. Saiai then asks Teitoku to which he gives an empty response, making Saiai even more wary against a Level 5 like him. Teitoku then asks where Rikou is, saying to her that if she tells her where she is he will her go. Saiai then asks if he thinks anyone would be stupid enough to go along with what he just said, to which he responds that there are, giving Frenda Seivelun as an example. Saiai is stunned is silence as Teitoku continues speaking. He says that he is simply giving her an option as she has no way of defeating her. Saiai does not respond to him, prompting Teitoku to ask again. Saiai then says that she doesn't have the right to refuse him with a smile on her face, to which she then grabs a nearby bench and threw it towards Teitoku. However, something explodes with Teitoku at its center, destroying the bench and blowing Saiai away 10 meters and then through a wall. Teitoku then comments on how her weighing her pride against her death was sentimental but unrealistic. Teitoku then orders a member of SCHOOL's subordinate organization to retrieve her. Surprised, the man asks if he know she's still alive, to which Teitoku states that's the kind of esper she is.

Teitoku later takes Saiai's unconscious body and after finding Shiage and Rikou dumps her body before them. Here, he praises Saiai for making the right decision and having Rikou get away as she is the core of ITEM. Apparently, for much of Shiage and Rikou's confrontation with Teitoku and later with the Girl in the dress, Saiai remained unconscious. It is only after SCHOOL left them, deciding that Rikou is doomed to her death due to the abuse of the Ability Body Crystal that she regains consciousness. She sees Shiage with the collapsed Rikou, and figures out the situation through Shiage's impatient demeanor. She tells Shiage to take Rikou and disappear. Shiage says thank you to Saiai, but she tells him that she didn't say as thanks. She says she was speaking ill of him as she doesn't need useless people like Shiage and Rikou in ITEM, as such she tells him to go out their way. There was a smile on Saiai's lips despite her injuries. Knowing what Saiai actually means, Shiage asks if there is anything she can do for her. Saiai orders him to contact their subordinate organization and call in the information suppression team and an ambulance, as she can't do it herself currently. Shiage complies, and later leaves Saiai. It is likely that Saiai was later taken to the hospital afterwards.

DRAGON Arc
In Volume 19, Saiai is hunted down by Stephanie Gorgeouspalace, who is intent on claiming vengeance for her partner Sunazara Chimitsu. Eliminating the source of Saiai's Offense Armor through repeated detonations of propane tanks in the Underground Mall, Gorgeouspalace corners the wounded ITEM operative and unloads with her weapon. However, as the dust settles from the monstrous effects of Gorgeouspalace's machine shotgun, Saiai is revealed to have survived the barrage with minor injuries, proceeding to incapacitate Gorgeouspalace with pistol rounds to her stomach and arms. Saiai reveals that she always keeps a canister of liquid nitrogen on her at all times, acknowledging Stephanie Gorgeouspalace's Anti-Skill training and her affinity for battling espers, as well as the fact that Gorgeouspalace had found her weakness. At the same time Saiai tells her that she is "...a person who has super struggled to continue winning and surviving,”— an esper like her would know exactly what she needed to do to compensate for her ability's shortcomings, and also that being a member of the dark side of Academy City means that it is not difficult to procure necessities for her work. Just before finishing Gorgeouspalace off, Saiai quips that for espers like herself, whose ability gives her incredible close-combat potency and defense, are far more threatened by combatants by snipers like Sunazara Chimitsu who can attack her from afar with impunity, rather than those relying purely on close-range firepower like Gorgeouspalace.

Freshmen Arc

 * Main article:Freshmen Arc

In Shinyaku Toaru Majutsu no Index Light Novel Volume 01, she is reunited with her friends from ITEM after the events in Russia. She later confronts the mysterious student, Kuroyoru Umidori, at this point it is revealed that Saiai was the "honor student" of the Dark May Project.

Homecoming Arc

 * Main article:Homecoming Arc

Ichihanaran Festival Arc

 * Main article:Ichihanaran Festival Arc

Eve of the Festival
Hamazura Shiage conspires with Kinuhata Saiai in order to have her accompany Kuroyoru Umidori to the Hero's Cave, a dentist clinic in School District 7, after noticing that she has been avoiding chewing with her back teeth. He installs gum into the ports where her nitrogen lances are fired out of, knowing that she would resist.

Saiai takes Umidori there, much to her horror, indicating that Umidori is still a child, predictably, she tries to oppose Saiai using her Nitrogen lances, but due to Shiage's countermeasures, it does not work, and Saiai forcibly takes her into the clinic.

Saiai later returns to ITEM's apartment building, and helps Shizuri clean the mess she made after she used her powers on Cendrillon. Saiai asks how it came to be, to which Shizuri bluntly tells the truth, confusing Saiai.

A half an hour before midnight, Saiai quickly goes outside of their apartment after hearing a ruckus, only to discover Mugino Shizuri before a middle-aged man wearing Frenda's clothes, who attacked her but was felled by her. Saiai notes this to Shizuri. Shizuri 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 Shizuri could still fight despite living a peaceful life away from the dark side. Shizuri 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 Saiai later dragged his ruin before a strange research facility, and tells each other to keep a secret from Shiage.

During the Festival
Saiai somehow ends up meeting up with Kuroyoru Umidori, Misaka 10032, and Misaka Worst, coincidentally, after the latter asks if there is anyone who else has nothing to do. Saia forms a disgusted expression after coming them, especially at Umidori. Misaka Worst, seeing her, agrees that she has that nasty look on her face, seeing at they are ken to the ways of the dark side. Seeing them all, Saiai then asks if they are a bunch of villains trying to create their own faction. Misaka Worst comments on how with dark people like them around, she could enjoy the Ichihanaransai honestly without holding back. Saiai manages to lose Misaka Worst, and once again meets up with Shizuri. Tagging along with her, they meet Shiage, Rikou, and Yoshikawa Kikyou, after they escaped from the revived Kakine Teitoku's Dark Matter beetles. Saia explains how they got here, to which Shiage explains to them the situation in "30 seconds." Shizuri 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. Saiai and Rikou frantically try to stop Shizuri from making Shiage worse off in her anger, but later tosses Shiage aside near a tree. Shizuri 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. Saiai just stands by as she watches step on Shiage as punishment after one too many dumb responses.

After that debacle, Saiai goes back to the apartment while the others search for Fremea. Despite being in the midst of the Ichihanaransai, Saiai is stuck doing the housework. During Shiage, Rikou, Kikyou, and Cendrillon's race back towards the apartment where the latter had left-over parts of her body, they meet Saiai cleaning up the apartment. She complains to herself about doing all the work, even though she handed off the dark side investigation to Shizuri, she is missing the Ichihanaransai. She leaps up after being heard by Shiage as she relieved herself by shouting, and beats him up with a wrestling move. It is implied that Saiai just watched as Cendrillon and the others realizes Kamijou Touma's final plan to stop Fräulein Kreutune from eating Last Order's brain.

She may have been left behind again after Shiage and the others quickly bring the brain back to Fräulein.

Agitate Halation Arc

 * Main article:Agitate Halation Arc

Saiai first appears in School District 13 on a stake out near Fremea Seivelun's dormitory with Hamazura Shiage to watch out for attacks from the remnants of Freshmen. Throughout all this, Saiai is unconcerned of the mission for Beetle 05 is with her, and preoccupied her time with the thoughts of her hobbies, the B-movies such as The Fiery Indian Cook Runs through New York and Saitama☆Vocal Crisis. Shiage, restless throughout the day, notes to Saiai that they are becoming complacent, though Saiai states that an attack from them is unlikely after they have defeated Kuroyoru and Silvercross. Shiage states that she isn't taking their mission seriously, to which Saiai points out that Shiage himself is also a hypocrite for always trying to partner up with Rikou. Tired, Saiai asks if they could end their routine as Fremea has the Rhinoceros Beetle as her guardian, attached on her backpack. Just then, right on schedule, Fremea's dormitory turns off its lights for the night. However, they then discover that Fremea turned her lights back on. Saiai tries to call her as she is still awake, but she doesn't answer. Suddenly, the alarm for the emergency exit in the dorm is activated, which confuses Shiage as Beetle 05 could've easily taken care of any enemy. Saiai however, doesn't care about the details and urges Shiage to quickly investigate what's happening.

As part of their investigation, they simply asked the dorm supervisor of what had transpired, and stated that there was no fire nor robber. In other words, they had learned nothing. Shiage and Saiai later hear the sound of explosions as the result of Kuroyoru Umidori's battle with Rensa, who has initiated another phase of her and Yakumi Hisako's plan. Fearing that Fremea is involved, they rush towards the sight of the blast. The both of them suspect the Freshmen, though they are open to any possibility. Suddenly, an exhausted Yakumi Hisako arrives, telling them to stop, though realizes that they would be the easiest hero to draw using Fremea Seivelun (relating to the Agitate Halation). This confuses Shiage, but Hisako too realizes that words have no meaning to "heroes", and decides to try a more convincing reason for them to give up.

Then, sounds of chaos erupts of all around them. Saiai warns Shiage that they are surrounded, and there they see innumerable cockroaches surrounding them, all under the control of Yakumi Hisako. The two are already disgusted enough but Hisako reveals that she has modified their brains to make eat anything and everything, even people. The man-eating cockroaches slowly approached them. As Saiai has the Offense Armor, she is protected from the roaches, and suggests Shiage to split up with her. Shiage hesitates but Hisako cuts into their conversation, warning them that it is a dangerous gamble as though they may not be able to eat a wall of nitrogen create by her Offense Armor, but she may not able to create the wall in the first place. Saiai points out that the conditions are similar to Hisako, as she too has something that protects her and sends orders to them. Shiage tries to stop Saiai from advancing, but Saiai points out that Hisako may have the ability to attack multiple places and that they can't leave Fremea unprotected. Hisako however taunts them of even believing that they can get away, but Saiai is unperturbed. Still confident, Hisako explains the reason she chose roaches is because the disgusting image they sow, causing more mental exhaustion than other insects like termites, and affecting her Personal Reality which controls Saiai's powers. The explanation alone was almost enough to overwhelm Shiage, but Saiai ignores it and tells him to run. Shiage still hesitates, but Saiai asks him if he is willing to let Fremea see the grotesque things that came from the dark side of Academy City. She reiterates that being the one that Fremea trusts is and is attached to the most, he has the obligation to live up to the trust, and that means not allowing her to see the things that the both of them have seen. With a nod, Shiage runs away from the battle, apologizing to Saiai, though she answers that she never even though he be any help.

Saiai's battle concludes after Rensa's defeat at the hands of Kamijou Touma. Saiai is coated with the liquids of the dead cockroaches, specifically her Offense Armor. With countless dead roaches, countless more swarm and consume the body of Yakumi Hisako. Saiai made used of the fact that she modified the air around her by simply using nitrogen for her Offense Armor. This allows her somewhat to control air currents through tactically calling in the nitrogen for her use, and allowed Saiai to destroy the optimal layout of the "scent" Hisako used to control her roaches. Thus, the cockroaches turned on their master. However, all the while Hisako being eaten alive, she continued to smile. Saiai asks her, unnerved by this. With a laugh, Hisako says that getting killed was part of her plan all along. Hisako boasts on how the plans they know of is not all of it, and scoffs at their ignorance. Saiai asks what her plan was to go so far to get herself killed like a disposable pawn, but Hisako just gives off a smug retort of asking the 7,500 "heroes" that have been summoned by Agitate Halation. Hisako "dies" with a smile, stating that the final phase is complete and the Agitate Halation Project comes into its completion. Saiai could not grasp when that woman had died as the roaches scatter away to parts unknown.

As the riots of the "heroes" reaches its climax in the Learning Core, Kamijou Touma witnesses the arrival (though they do not know them) of Kinuhata Saiai with Takitsubo Rikou and Mugino Shizuri, the latter destroying Fusuo Ayame's (one of the "heroes") trucks that apparently allowed her to use her power. They have apparently come to look for Fremea Seivelun based on the information given by Shiage. Shizuri frowns on Shiage's troublesome disposition, as he asked for help but did not give them better information. Saiai states that they will Fremea eventually after they defeat all of them. Rikou then detects a signal from south-southwest, most likely Fremea's AIM diffusion field. However, Ayame comes upon them, still unperturbed by the destruction of her trucks, though she is quickly dispensed away by the arrival of Sogiita Gunha.

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 Shizuri regarding her preference with the salmon bento, forcing Shizuri to fire back with a criticism regarding Frenda's preference for canned foods. Saiai comments on how both of them are focused on seafood and that they should make their characters more distinct. Rikou 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. Saiai 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.

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

After St. Germain has sealed the Dianoid, Saiai checks the exits and finds that they have been fused. Saiai 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, Shizuri decides to create an escape route using her Meltdowner. Despite firing several times on Dianoid's walls, it simply regenerates. Rikou and Saiai chastises her for continuously repeating her actions. Rikou then asks what they should do next leading to Shizuri to once again continue trying to use her Meltdowner on the Dianoid, much to Saiai's chagrin.

After St. Germain notices Shizuri's incessant attacking of Dianoid, one of them confronts ITEM himself. As he rambles on about his plans, Shizuri orders Saiai to protect Rikou. Shizuri 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, Saiai 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". Rikou then tells Shizuri 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 Saiai using her Offense Armor, while Shizuri 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. Rikou 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 Shizuri'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. Rikou asks what they should do, to which Shizuri 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, Shizuri attacks, nearly hitting Shinka in the process. Shiage calls out Shizuri on this. She justifies it as she still believes that Shinka is still in the enemy's side. Shiage notes that Shizuri 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. Shizuri just sighs and just attacks St. Germain instead. Rikou 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..

Mugino Shizuri and Kinuhata Saiai assist in the battle using their esper powers, trying to thin down the horde of St. Germain's and their plant matter beasts created through their magic over carbon. During the battle, Shizuri uses her Meltdowner to burn the carbon monoxide that was filling the basement that was being produced by the carbon creatures made by St. Germain. As the battle continues, both Shizuri and Saiai are able to take down several St. Germains though not as much as Stephanie Gorgeouspalace. However, when Shiage moves into Shizuri's line of fire, Rikou uses her powers on her before she could even fire. This surprises Shizuri, but Saiai snaps her back into fighting the St. Germains again. It is shown that ITEM is buying time and providing "samples" for Index and Othinus to figure out a countermeasure against St. Germain. It succeeds, as Index is able to sing a song that slowly unraveled the structure of St. Germain, and later allowed Shinka to put the finishing blow.

After the defeat of St. Germain, Saiai and Shizuri are carefree regarding the graviton-style base isolation structure making strange noises and spewing steam, and urges Shiage and his Power Lifter to do something about it. He is later forced to use his Power Lifter to hold down the places were steam was coming out as Shizuri and Saiai leaves, complaining about the awful day they just had.

Level Upper Arc

 * Main article:Level Upper Arc

Saiai and her comrades in ITEM appear in a Joseph's Coffee and Restaurant. In both the manga and the anime adaptation, she can be seen here reading a magazine. In the manga, they argue about whether or not they should all go to a pool since it's summer when they take notice of the Level Upper treatment program being broadcasted all over Academy City.

Sisters Arc

 * Main article:Sisters Arc

She and ITEM are later seen finishing up one of their missions while still arguing over the swimming pool debate, when Shizuri gets a call to protect a research facility that is being targeted by Misaka Mikoto. Shizuri orders Saiai to check the establishment and find out if the attacks are simply a diversion. Saiai observes this to be true when she discovers and detains Nunotaba Shinobu who was trying to install certain emotions into all the Sisters, but Shinobu ultimately fails as Last Order had acquired all the data, thus stopping it from spreading throughout the network.

Saiai is later seen calling Shizuri (who is in a fierce battle with Mikoto) to tell her that their part in the mission is done. After this, she appears once more, telling Frenda on the behalf of Mugino that Frenda should be prepared for punishment.

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.

Saiai briefly reappears on September 2, while relaxing in ITEM’s private swimming pool together with the other core members of the organization.

Toaru Majutsu no Index Light Novel Volume SS2

 * Main article:Toaru Majutsu no Index Light Novel Volume SS2

The First Friday of October
Shiage's first job as a member of the subordinate organization for ITEM is to forge an ID for Kinuhata Saiai to fake her age as she wants to watch an R18 movie. With that done, she later takes Shiage with her to assure that her cover that she is of mature age holds up. After going through backalleys they eventually come upon a secluded theater that showed specialty films.

Entering the small theater, Shiage asks Saiai why no one is there fifteen minutes before the movie starts. A great sigh escapes Saiai, surprising Shiage. Here, Saiai discovers that since she is the first guest of the exclusive screening then it means she's the only one that truly understands how great the film they are about to see truly is. Here, she laments on how it feels like she is the only the director is trying to reach through the film. After buying some popcorn, Shiage finds the already seated Saiai mocking his choice of popcorn, saying that it makes one thirsty. In spite of this, Saiai consumes the popcorn he brought. Shiage shows that he has brought a drink, to which Saiai mocks though at the same time drinks it.

As the movie starts, Shiage questions the quality of ther production. Here, Saiai lectures him that B movies like the one they are watching is supposed to be poor of production. Shiage asks why they couldn't just watch a normal movie in a normal theater. Saiai says that though the huge hits may break records over and over again, but a good B or C movies will stick with one more. In spite of this, Shiage just sighs and says he doesn't understand it.

Hearing Saiai's words, Shiage thinks that it can apply to espers as well, wondering how many espers had undisplayed abilities that were hidden because the city lacked budget, staff, or the proper facilities and equipment. He then wonders about his own powers, about Saiai's own powers, as well as the possibility that people outside the city displayed powers that can rank then amongst the Level 5s. As these thoughts fill his mind, he projects his feelings regarding espers to that the film, and became more interested in the film he is watching with Saiai.

Believing that he now understood Saiai he looks to her. Much to his surprise, she complains on how the film is boring. Annoyed, Shiage complains about her attitude and asks for her to at least pretend she is enjoying the film. Saiai explains that she thought that it would be good but became disinterested after 10 minutes. Shiage complains about how he felt he understood B movies and the growing sense of identity he had with it. This just confuses Saiai, asking what kind of understanding he can get from the terrible movie they are watching. Having loss empathy for the heroine in the movie, Saiai estimates her time of death. Shiage protests, saying the heroine will survive the movie. Hearing this, Saiai proposes a bet, wagering a pack of gum.

Needless to say, Shiage immediately loses after the heroine is eaten in the movie, much to Saiai's delight.

The Second Friday of October
After the Sisters rescue the 50 Gemstones that were gathered by different organizations scattered around the world that was started by George Kingdom, Kinuhata Saia is hired by Kumokawa Seria to assassinate him. Arriving to where the man is hiding, she complains that she has to take care of a fat old man who is misunderstanding things. She then says that once she is done she can go watch movies that aren't released in Japan. Before he could turn around Saiai kills him.

Offense Armor
Kinuhata Saiai's ability is known as Offense Armor (窒素装甲 (オフェンスアーマー) ). At Level 4, the ability allows Saiai to control the nitrogen in the air in order to create a thin barrier around her. It is the result of the horrific experimentation done to her in the Dark May Project, where a portion of Accelerator's thought patterns were inserted into her brain. Apparently originally an atmospheric control-type esper, this process allowed Saiai to gain a rapid increase in the strength in her powers, though at the cost of the stability of her personality. Here, Saiai received an idealized version of Accelerator's Redirection, and like Accelerator's this gives her the ability to create a barrier around her, though now instead uses super-compressed nitrogen instead, which is the primary function of her ability as defensive capability. Her power creates a barrier 360 degrees around her body, and also activates automatically without her wanting to. The armor is very effective, allowing for bullets from handguns to sniper bullets to be unable to penetrate her.

A secondary capability of her ability allows her to control compressed masses of nitrogen, allowing her to lift heavy objects like cars and deal powerful blows that can destroy entire walls. However, her effective range is very small as it only extends a few centimeters from her palm. She is also somewhat capable of manipulating air currents via displacing the nitrogen, which she uses for her Offense Armor. This is the method that allowed Saiai to confuse the man-eating cockroaches of Hisako, disrupting the scents that is used by Hisako to control them, and allowing her to make them turn on her.

A weakness of this ability is that a sufficiently powerful force can just knock her down due to her small body, as with the case against Sunazara Chimitsu's sniper rounds, and Umidori using thousands of Bomber Lances on her, or even pierce it such as Teitoku's counter against her using a bench against him.

Saiai acknowledges the defensive limits of her Offense Armor later, where where she is confronted with the sheer destructive power of Stephanie Gorgeouspalace's light machine shotgun. She notes that taking more than seven bullets at less than five meters of range would be "super bad". By the end of their fight Saiai incurs several injuries, though none are life-threatening. In order to compensate for foes who prove to be able to eliminate naturally-occurring nitrogen in the air like Stephanie, Saiai carries around a small canister of liquid nitrogen for use at all times.

Other abilities
She is a capable marksman, able to use handheld missiles to accurately target an enemy from a few hundred meters away while being shot, as well as shoot at a moving target accurately from a moving car.

Design evolution
Saiai's design remains the same throughout the series. However, Haimura states that Saiai's age has been different when he designed her, and as such she looks a lot younger in the novels.

Quotes

 * (To Shinobu, from Railgun Chapter 29): "My Offense Armor won't break to mere guns."
 * (To Shiage, from Index Volume 15): "So bunny girls are a super hit with you, Hamazura?"
 * (To Shiage, after telling Hamazura to take Takitsubo and leave ITEM behind due to Takisubo's condition. ibid): "I didn’t say it for thanks. I was speaking ill of you. We don’t need super useless people like you and Takitsubo-san in ITEM so I’m telling you to get out of our way."
 * (To Shiage regarding her sweater dress, from Index Volume 19): "Isn’t it super amazing that you can’t see it even when I’m in this pose? This angle is super different from your everyday bitch."
 * (To Shiage, ibid): "For the bunny girl-crazy super pervert Hamazura, giving any sign that you are losing your respect and fear for us is a crime. Is that super clear?"
 * (To Shiage, ibid): "It’s 100,000 years too soon for a sexual animal lower even than a caveman to super debate whether I, Kinuhata-sama, am sexy or not. To be blunt, you’re super too full of yourself. You need to at least evolve further as an animal first."Hamazura stated that she couldn't pull off sexy looks in a bunny costume.
 * (To Shiage, ibid): "Hamazura!! Super run away!! I doubt they’re after me!! They’re after you!!"
 * (Regarding Mugino Shizuri, from NT 1): "Oh, so you even super looked into all the people Hamazura knew? Yanderes can be super scary."