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 being not being saved by Touma due 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 was drawn into Academy City's dark side and came to resent Misaki not just for stealing her chance to become Level 5, but also for being saved when she wasn't.

Shundou Toshizou would later make use of her, manipulating Ayu 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.

In the hopes of tormenting Misaki and eventually confronting her for her revenge, 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. To support this, 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.

Shokuhou Misaki Arc
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. Following the removal of the Strobila, Ayu had several of her subordinates approach Misaki disguised as Emergency Aid workers to replace it under the guise of treatment for instability.

When 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 Misaki, who realized that her enemy had arrived and took out her remote. After first appearing to her with a generated image, Ayu confronted Misaki from behind. Seeing the huge mass in front of her in a Tokiwadai uniform, Misaki questioned if she was really in middle school, 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.

Ayu then began her attack, turning Misaki's arm black with the dust and setting a swarm of hornets on her, but a member of Misaki's clique incinerates them with a mass of flames. After marking her location with the magnetically-controlled monitor, Ayu wondered where the other hidden pawns are, recalling that Misaki can only accurately control up to fourteen people at once and threatening to cut off her arms and legs, leaving just her brain that can't crawl. After Misaki made another failed attempt to control her, Ayu had the dust create the image of a swarm of insects crawling up her feet towards her neck, describing the primitive fear that can't be avoided even if one knows that something isn't real. She then had a giant eyeball appear on her flesh and freeze Misaki with fear, comparing it to of Greek mythology. As Misaki doubled over, she had another clique member create an electric discharge, disrupting the monitor dust temporarily. Marking the second one, Ayu asked how many more there were, saying that she could crush them as long as she knew where they were and adding that Misaki couldn't stand to see one of her pawns die despite arrogantly controlling people. 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.

Wondering who her enemy was, being familiar with her past and powers and being able to outdo her in psychological warfare to such an extent, Misaki asked her if she had some connection to her, to which Ayu replied that she did as otherwise she'd have no reason to resent her and when Misaki said that she'd never met her, said that if she had met her, she wouldn't have been able to resist killing her then. On being told she was insane, Ayu laughed and asked who can prove that people like them who readily manipulated people's minds still had sounds minds of their own. As Misaki faced her, Ayu began to alter the surroundings again, but to her surprise Misaki started to throw her remotes at her face. As Ayu covered her face, Misaki got closer to her and grabbed at her neck, pulling out a Strobila embedded in it. Thinking that she'd removed Ayu's means of resistance, Misaki used her ability again and Ayu pretended to have fallen under her control.

Unable to gather her enemy's thoughts, Misaki asked Ayu several questions with her remote. Ayu told her that she was the only one giving orders, working alone but controlling useful assets to give the illusion of an organization and using the FIVE_Over OS to control them, as well as explaining what it was. She then told Misaki that she was doing this for revenge and to punish her for stealing 'her'. Misaki asked her who she was and Ayu claimed, to her shock, that she was Shokuhou Misaki.

Under the impression that her foe was under control and could not lie, Misaki questioned her further and started to wonder what was going on, but as she was floating in doubt Ayu caught her with one of the FIVE_Over's tentacles, laughing that she had told her that her ability wouldn't work. After the FIVE_Over OS unit split off from her, she appeared in front of Misaki looking exactly like her, before having her face melt away. 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, which she confirmed, telling her that her ability was Mental Stinger, stuck at Level 3 but originally meant to reach Level 5. She then asked if Misaki had heard about the Parameter List, the document determining who to focus on and who to discard, introducing herself to her as the ant who could not become the bee, the other fruit cut from the branch to let Misaki grow.

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 are also capable of resisting it. Similar to Shokuhou Misaki's use of remotes for Mental Out, Mitsuari Ayu sets targets for Mental Stinger with 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 Designer's 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.