Mitsuari Ayu

Mitsuari Ayu (蜜蟻愛愉) is a character introduced in Shinyaku Toaru Majutsu no Index. A Level 3 esper with the ability Mental Stinger, she bears an immense grudge against Shokuhou Misaki, who was chosen over her to be developed to Level 5 and was saved by Kamijou Touma when she wasn't. She is the main antagonist of the 11th Shinyaku Toaru Majutsu no Index novel, and represents a contrast to both Misaki's situation and character.

Etymology
Her family name, Mitsuari (蜜蟻), means. Continuing with her contrasting character to Misaki, her given name Ayu (愛愉) means "love" and "joy".

Appearance
Mitsuari Ayu has long, wavy, chocolate-colored hair, apparently as fluffy as cotton candy. She has smaller breasts than Shokuhou Misaki but apparently has more beautiful legs than her, more than just long and slender. She wears a special, dark suit, resembling a racing swimsuit, with similar gloves and boots.

Personality
Due to not being saved by Touma in contrast to Shokuhou Misaki, who was saved by him and was also chosen over her to become a Level 5, Ayu bears an immense grudge against Shokuhou Misaki, to the extent that she wishes to steal the happy memories that Misaki has of him for her and her alone.

Background
In the past, Mitsuari Ayu and Shokuhou Misaki were found by Tree Diagram to both have the possibility of reaching Level 5, possessing abilities with a near identical basic theory and scope, though they would plateau at Level 3 under standard curriculum. The higher-ups decided to prune one and focus on developing the other. Following the Parameter List, they chose to focus on Shokuhou Misaki, with Mitsuari Ayu being kept as a back-up in the event of her death.

A year before the current year of the Story Timeline, Mitsuari Ayu had encountered Kamijou Touma. At that time, her circumstances had driven her to consider suicide. When she was about to go through with it, she sent a message to Touma, hoping that he would save her. However due to bumping into Shokuhou Misaki at an intersection, Touma lost his phone and as such was unable to reach her in time. Though her suicide attempt at Ground Geo failed, Ayu came to resent Misaki not just for stealing her chance to become Level 5, but also for being saved when she wasn't.

At some point in her desirer for revenge she drew herself into Academy City's dark side and where Shundou Toshizou would later make use of her, manipulating her and without noticing for the purpose of finally stealing Mental Out for himself. It is likely that much of the equipment that Ayu acquired came from him like how he supplied Deadlock before.

Mental Out Arc
In the hopes of tormenting Misaki and eventually having Misaki erase her own memories of Touma in the belief that it was false, Ayu used the FIVE_Over OS along with her subordinates to camouflage the Ground Geo power station in order to make Misaki suspect that her memories had been tampered with and use her own ability to change them. After Misaki discovered that the geothermal station was different from her memories and doubting them, moved to find out who was responsible, Ayu started to make her move as well. To support this ruse, she altered the files about the station and secretly had a Strobila embedded in Misaki's neck, without data and meant to reinforce her doubt. When the Strobila was removed Ayu had several of her subordinates approach Misaki disguised as Emergency Aid workers to replace it under the guise of treatment for instability. After this plan failed and Misaki discovered that the whole geothermal station had been covered by camouflaging dust, Ayu, in Ground Geo's monitoring station and wearing the Outsider suit, decided to take action. After contacting her subordinates and confirming that the FIVE_Overs were going to be ready, Ayu turned to Misaki on the monitor, telling 'Miss Bee' that she stole her so it was time she was punished.

Using the cover of the camouflage, Ayu approached appearing to her with a generated image, Ayu confronted Misaki from behind. Seeing her as a huge mass in a Tokiwadai uniform, Misaki questioned if her appearance was genuine to which Ayu responded that she could ask the same. When Misaki attempted to use her ability on her, Ayu told her that it won't work and that she wouldn't have shown herself if she thought it would.

As their fight began a large burst of flames hit the magnetically-controlled monitor disrupting the illusion, Ayu then realized that it must be the work of Misaki's group and then began wondering how many more were in the area. Following another failed attempt by Misaki to control her assailant which resulted in the creation of a new illusion from the dust paralyzing her with primal fear. As she doubled over an electric discharge disrupted the monitor, aware it was the work of Misaki's group Ayu demanded to know how many others were there and threatening to crush them knowing that Misaki couldn't stand to see her "Pawns" die. Seeing her reaction, Ayu wondered if the look on her face meant that she had ordered them all to withdraw, which saved her the trouble.

Misaki then asked her if she had some connection to her, as she was not only familiar with her past and powers, but was able to outdo her in psychological warfare to such an extent. Ayu replied that she did as otherwise she'd have no reason to resent her despite never meeting each other before, saying that if she had met Misaki then she wouldn't have been able to resist killing her. Misaki responds calling her insane, Ayu laughs and asks if people like them who could so readily easily manipulate the minds of people still had sounds minds of their own. As Ayu began to alter the surroundings again, Misaki who had readied her self began throwing her remotes at Ayu, catching her surprised as she covered her face Misaki got closer to her and grabbed at her neck. After pulling out a Strobila embedded there, believing that she'd removed Ayu's means of resistance, Misaki used her ability again and superseded to question Ayu after discovering she was unable to gather her enemy's thoughts, who then pretended to have fallen under her control answering all of Misaki's questioning. She then told Misaki that she was doing this for revenge and to punish her for stealing 'her'. Misaki then asked her who she was and Ayu claimed, to her shock, that she was Shokuhou Misaki. With Misaki was under the impression that her foe was under control and could not lie, she pushed her questioning of Ayu further in a hope to discover what was going on. As Misaki was clouded in doubt Ayu caught her with one of the FIVE_Over's tentacles, the FIVE_Over OS unit split off from and the Designers' Gel melting off her to reveal herself for the first time before her rival. As Misaki cried out, asking who she was, Ayu asked if she still didn't know, revealing her true appearance to her. Though Misaki didn't recognize her, she sensed that Ayu was similar to her, Ayu confirmed telling her that her ability was stuck at Level 3, but originally meant to reach Level 5. Ayu then asked if Misaki had heard about the Parameter List, the document determining who to focus on and who to discard, referring to herself as the other fruit cut from the branch to let Misaki grow.

She then likens their relationship to that of Shirai Kuroko and Musujime Awaki and that the reason Misaki's powers fail to affect her is simply because they are similar allowing for her to interfere with its workings. Misaki then starts to deconstruct Ayu's reasoning on her grudge pointing out its flawed nature and using Touma as an example of his determination dispite being a Level 0. Ayu merely laughs and she praises Misaki before revealing that she not only knows Touma, but her real reason for seeking vengeance is because she was not saved unlike her and that it was Misaki's fault. While saying this she grabs the sides of Misaki's head with both her hands holding a smartphone, devices she uses to control her power like Misaki's remote controls, and presses her forehead together with Misaki's to use her Mental Stinger on her, giving Misaki a strange sensation. In spite of this, Misaki points out her action's futility as having the same type of power any interference can be deflected, but Ayu believes it, saying that it's true only if both reject it and then asks Misaki what will happen if she accept it instead. Misaki then realizes Ayu is not directly using her power on her mind, but rather as an ignition to make her lose control of Mental Out to which Ayu confirm saying she is using Misaki's power to drag her in her head, which she succeeds in immediatly after.

After Misaki's consciousness is trapped in her mind, Ayu explains the details of her attempted suicide at the power station, where three days following his failure to save Ayu Touma meets Misaki about to erase her memories. Ayu explains further that the reason Touma was not able to save her was because of him losing his cellphone when they first met bumping into one another. After finishing her story Misaki asks her on the reason she is wearing the Designers' Gel suit, and Ayu realizing the true question answered that she did not want Touma to know that she was still alive, but had fallen to such a level. After hearing this Misaki then declares that she will save her because it is what Touma would do.

Trapped within Mitsuari's mind, Misaki tries to figure out Mitsuari's motive despite the fact that Ayu can read her every thought. In spite of her taunts, Misaki determines that Mitsuari's revenge is beyond just simply killing her though it was too late, as Mitsuari Ayu herself reveals that she has bought the needed time and her trap is no longer needed. Much to Misaki's horror, the FIVE_Over Modelcase Mental Out appears before her. Ayu explains to Misaki that it is not functioning as intended as it cannot replicate her powers and as such she will complete it by putting Misaki inside the machine, and then she will finally use her own Mental Out to destroy Misaki's memories with Kamijou Touma. Though Misaki is trapped physically in the real world by the OS and mentally by Ayu's powers, she still has a trick up her sleeve. Using her clique to attack the people who are providing the Five OVER Out Sider's viewpoints that allow it to create its illusions, allowing her to hijack the lenses to provide malicious feedback to FIVE_Over Out Sider, allowing the clique to take control of it.

With the OS now under her control, Misaki uses it to attack Ayu. In turn, Ayu also uses the FIVE_Over Modelcase Mental Out to counter it. The battle turns into a physical confrontation between Misaki and Ayu, and though Misaki tried to use OS to create illusions against Ayu. However, Ayu manages to use her phone to filter out what she sees. In the end, Ayu manages to hit Misaki's head and used her smartphone to finally beat her, knocking her unconscious. As Misaki awakes paralyed inside the capsule of the FIVE_Over Mental Out, due to being submerged in conducting fluid, Ayu is busy connecting electrodes to her body for the machine. Despite this, Misaki tells Ayu that Touma will come to save her in spite of all odds, as he is her hero. Misaki then blows the whistle Touma gave to her, enraged by this Ayu tries to strangle Misaki, rationalizing that though Touma may be a hero he isn't almighty and that she is an example of that limitation. However, beyond all hope, Ayu's expectations are overturned at last and Touma finally arrives as if to answer Misaki's call. Ayu then breaks down at the sight of Touma's arrival, making her ability go haywire, though Touma easily negates it. Touma later helps resolve the conflict that happened there in the name of the memories that they had for him that summer a year ago. Misaki then tells Ayu to get saved by Touma as she has been saved enough. Regardless, Ayu truly was saved. Misaki later mentions Ayu has been “officially” sent to the Reformatory, though her eventual fate may be unknown due her reckless actions, and that they may need to watch over her to protect her from the darkness.

Abilities
Mitsuari Ayu's Level 3 ability is Mental Stinger (心理穿孔 (メンタルスティンガー) ), which operates in a similar way to Mental Out. Originally thought to manipulate the brain by controlling bioelectricity, it actually does this by manipulating moisture, controlling the distribution of fluids and the secretion of chemicals in the target's brain. Instead of directly controlling bioelectricity, it changes the conductive efficiency by controlling the fluid acting as a catalyst for it to flow through - as such, the ability doesn't work on espers that directly manipulate their bioelectricity such as Electromasters, though it is speculated that this can be overcome with an increased output. Abilities of a similar nature, Mental Out, are also capable of resisting it, though this happens only if both Ayu and Misaki reject the interference. If Ayu accepts it intentionally opening a port and allowing an exchange of identically-formatted packets she is able to drag Misaki's consciousness in her mind using the Mental Stinger as an ignition to make her lose control of the Mental Out. Ayu accomplishes this placing both her hands holding a smartphone on the sides of Misaki's head and pressing their foreheads together causing Misaki to feel a strange sensation like invisible wires running through her head had been gathered together and suddenly pulled out from her forehead. Like Misaki, Ayu sets her targets for Mental Stinger with a device, in Ayu's case, smartphone cameras and her fingertips.

Under certain circumstances such as extreme anger, the ability can go out of control and cause an explosive phenomenon similar to freeze-drying that creates a territory that can cause any living being within it to crumble like dried paper mache.

Equipment

 * FIVE_Over (Outsider) - Modelcase_"MENTAL_OUT" (ファイブオーバーOS(アウトサイダー)): Like other FIVE_Overs, this is meant to reproduce a Level 5's power with pure technology, though the OS (Outsider) indicates that it exists outside the mainstream method, using methods different from a Level 5's power to produce the phenomenon resembling it. In this case, magnetically controlled monitor dust is distributed across an area and used to alter the appearance of the target's surroundings, using that twisted information to influence their mental state and memories. The device is still a prototype and has plenty of problems remaining, hence why it hasn't been mass-produced. The base unit is a spherical device, taller than a person, with tentacles extending from its bottom half, resembling an artificial octopus. It is constructed from an artificial fat called Designers' Gel which is capable of changing shape. It has numerous large eyeballs on its surface, which roll and blink, perhaps due to the magnetically controlled monitor. Five_Over (Out_Sider). Modelcase_"MENTAL_OUT". is written on the side of its tentacle. The Outsider can also take the shape of a large wearable suit, forming a body that should weigh around 300kg were it real.
 * The magnetically-controlled monitor (磁性制御モニター) that is used by the Outsider primarily consists of colored powdered dust, which is scattered throughout the target area and controlled via magnetism. It is capable of changing in real-time, altering the surroundings around the target to influence them. An example of this would be producing images of insects to induce revulsion and fear, or an eyeball with a gaze that paralyzes those that see it, much like Medusa in Greek Mythology. It is even capable of creating sound by rubbing together like cricket wings. However this system requiring a network of multiple viewpoints other than that of the user to perfectly overwrite the surrounding area in real time, which can be used by an enemy to manipulate the Outsider by feeding it with malicious information.


 * FIVE_Over Modelcase_"MENTAL_OUT" (ファイブオーバー モデルケース・メンタルアウト): Ayu's trump card against Misaki, a machine which is supposed to recreate and surpass Mental Out using technology. However this particular machine doesn't strictly fit the definition of FIVE_Over as it doesn't contain anything to reproduce an esper ability using technology, instead containing 8000 output devices, with the intention to have Shokuhou Misaki placed inside and her power drawn out forcefully, in order to acquire the sample data to complete and mass-produce it, as well as to crush Misaki's mind with her own power. Resembling a scorpion wasp, its main body is 4m long with six legs and thin wings 8m long when extended. Its abdomen is translucent and filled with anesthetic conducting fluid, meant to contain a human body, and ends with a stinger formed by a tube that extended more than three times the length of its body, resembling a scorpion wasp’s ovipositor, which can be used as a weapon. It can be programmed to act automatically.


 * Strobila (ストロビラ): A device intended to manipulating the mind without interfering with the brain. It is consists of a very small plastic core with a long fiber that leads to the subject's heart and affects the secretion of hormones. Strobilas were installed in Misaki and Ayu's Outsider body as decoys.

Design evolution
Mitsuari Ayu's character design is basically the rejected initial design for Shokuhou Misaki, with a few changes to her expressions due to her psychotic 'yandere' tendencies. According to Haimura Kiyotaka, rejected designs are normally locked away however the story in this case was written using the concept of an unfortunate girl who could not become Misaki, allowing that rejected design to be made into a character.