Amahebi Saeka

Amahebi Saeka is an Academy City student who created ExitApp (イグジットApp).

Appearance
Amahebi has long bleached blonde hair and brown-tanned skin, like other gyarus in School District 15. She also wears a light-colored school uniform, presumably a high school one, with a short skirt.

Personality
Amahebi loathes her esper power, both for the poison aspect and how it makes her blood weird colors, and her complex over this was what prompted her to seek a tool capable of changing it, which would eventually lead to the development of the software which would eventually become ExitApp. She also hated the spread and use of the adaptation of her failure for suicide and people profiting off that, and was horrified when someone expressed the intent to use it for murder.

Background
Amahebi developed the software which would become ExitApp as part of research into changing a person's esper power. The modified health management software was meant to be a type of Testament which used the massage chair's electrode sleep assistance. Rather than a conventional Testament affecting the 'software' that are a person's memories, ExitApp was meant to affect the hardware that creates an esper power, freely choosing which parts of the brain's synapse wiring to cut off and manipulating the structure. Her short term goal was to change the basic type of a power, with a long term goal afterwards to allow adaptable changes so one could switch between powers on the fly, a version of Dual Skill. However, the experiment in cutting off synapse signals went wrong and failed at the first step, with an uncontrollable bug causing the chair (not just the head) to move beyond its design limit, with fatal results.

Amahebi shut down the project, however many people wanted the failure she had created and the program leaked out, resulting in the distribution and use of ExitApp. With no way to fully erase it from the internet, Amahebi uploaded many fake tools and codes with similar structure but no effect, as well as false information about the use of caffeine or catechin instead of the alcohol it was never designed to to be used with, however people still searched out the deadly combination from the misinformation. She would subsequently target people selling and profiting off the suicide tool, taking down several sales routes, but was seen in the area a couple of times by customers, who learned she was the developer and would attempt to get to her.

Toaru Kagaku no Railgun (light novel)
Around the same time as Amahebi was trying to shut down the sales routes for ExitApp, Anti-Skill was running an investigation into suicides connected to ExitApp. In addition, although not a Judgment job, Shirai Kuroko and Uiharu Kazari, along with Misaka Mikoto, were also looking into the case. With Mikoto and Kuroko having made a scene while crushing the sellers distributing modified versions, the parties involved were on alert for them, so they stayed behind as back-up while Uiharu proceeded with a sting operation. Amahebi ran into Uiharu, with the two going underground.

With both unaware of who the other was and their true intentions, Uiharu posed as someone offering to fix a security hole in the seller's system and make a profit. Believing her story, Amahebi slammed her to the wall, revealing that she was ExitApp's developer and was working to crush those trying to profit off the suicide tool. Noticing customers coming, Amahebi decided to show Uiharu mercy and take her with her, but Uiharu managed to get her taser working and used it on her.

On learning that Uiharu was actually from Judgment and realizing that she had the situation entirely wrong, Amahebi introduced herself and explained the circumstances behind ExitApp. When Uiharu proposed a way of stopping ExitApp, they were confronted by Maki, an unstable customer who sought to use ExitApp to kill a woman and make it look like suicide, to Amahebi's horror. When Maki brandished a metal tape, Amahebi stood in front of Uiharu and on being cut, used her blood to incapacitate Maki with her ability. She was then dismayed to find that a drop inadvertently fell on Uiharu and poisoned her as well, but Uiharu convinced her that she could use her ability to counteract the effects in a similar way to the proposed solution to ExitApp, turning her poison into a medicine.

Abilities
Amahebi's ability is Scorpion Tail, a type of reverse psychometry which allows her to seal an image in her head into her blood and forcibly send it into the minds of those who touch the blood, in her case reproducing the effects of poisons through deadly images. This includes existing chemical poisons, as well as legendary poisons that might not exist. As a result of her ability, Amahebi's blood constantly shifts through many colors.

She also has a degree of programming skill, with her modification of an IoT massage chair health management program to create the software which would form the basis of ExitApp, as well as measures taken to mitigate the spread of ExitApp.