System Scan. The <<best>> way to detect hidden abilities in students. It was created by the top of Academy City's scientific teams and could elaborate at high speed the data received from a child, printing the full analysis over a digital document that would be sent to the main Academy City Databank. Its programming was flawless, its analysis precise and the delays were absent. Why did I say <<best>> between quotes earlier, then?

Well, System Scan had a flaw. A terrible flaw that no amount of coding could fix: it was a machine.

Before research lab M-25 found evidence of telepaths who could communicate with animals, it was simply assumed that abilities were limited to physics related feats like thermodynamics and electromagnetism.

System Scan used to work like this: the machine would send specific signals to the subject's brain, in order to stimulate certain areas. Then, based on the neurons' response, it would elaborate what kind of ability the subject had, or could develop. The main issue with this was, as I said, the mechanical nature of the machine: as such it was impossible to detect those abilities revolving around living things. It's actually quite simple: how could a machine, which had no organic cell, detect any change when the ability user required organic cells to activate their ability?

So, until research yielded irrefutable proof that telepaths indeed existed, nobody had any idea they were even a possibility.

Even then, the issue was still finding those ability users with something more efficient than a series of tests carried out by an entire team of scientists for days. Not only it was inefficient, but Academy City lost a few great minds working in said teams due to the incapacity of some kids to control their powers.

At first, at the time System Scan 1.3 was developed, it was suggested to add a certain amount of organic matter in System Scan, to allow the machine to detect those subtle changes caused by ability users. This helped a lot, but tests still had a hard time revealing abilities concerning specific and rare animals. For instance, the first telepath that could read armadillos' memories spent over 5 years believing he was a level 0, until by chance he happened to meet one during a trip to the zoo. Since the boy was only able to read information from an armadillo's brain, the organic matter inserted in System Scan 1.3 remained untouched.

Now, inserting every possible type of organic matter in System Scan was simply unfeasible, so animal telepaths remained mysterious and were often undiscovered until some random occurrence happened.

...that is, until Ability Scanner appeared. You see, Ability Scanner was an ability invisible to System Scan, as it required other abilities to trigger it, and System Scan had no ability. Just a few kids claimed they could sense other people's abilities, regardless of the type, and most of them never failed. A bunch of kids could in fact do what even the best machines couldn't! Teams of the best scientists tried to unravel the mystery behind Ability Scanner, the one ability that could detect and, when at higher levels, analyse any other ability. Loads of money were spent in funding this research that would allow Academy City to jump 10 years in the future. The simple concept of seizing the way such ability worked motivated scientists to realise the oddest experiments and, in some cases, the least moral experiments took place.

To these days, decades after finding Ability Scanner, none seemed able to copy it, nor to clone the user while retaining the ability. It just still can't be done for some reason.

Even how it worked was still unsure. The best theory was that Ability Scanner users could read the AIM diffusion field constantly generated by espers, and could elaborate that.

Now, those years weren't fruitless anyway: research allowed the creation of machines that could detect the AIM field, even without being able to elaborate that deeply. This proved the existence of said field, which used to be nothing more than a theory. Trained Ability Scanner users were incredibly helpful in finding esper powers and collecting data on them.

Thanks to these trained users, the number of espers with a known ability doubled within 5 years, decreasing the rate of level 0s from 85% to 70% of total students.

It went on like this for a decade.

Until System Scan was updated to version 2.0.

Ten years after discovering Ability Scanner, research team G-10 managed to find out exactly what part of the user's brain allowed them to elaborate the AIM diffusion field data.

System Scan 2.0 was finally able to detect all known abilities (and is, in fact, still used today, even though we call it simply "System Scan", without mentioning the version). An incredible improvement: it wasn't required anymore to train kids when testers could simply download all the important data in a machine that could take measurements all day and night without breaks even though, as expected, the brain of the machine was, and still is, partly mechanical and partly organic.

Soon, Ability Scanner users lost the only use they had as human beings in the eyes of the City's council.

Not many people know this story. Well, I'm not surprised that you never saw an Ability Scanner user in Academy City. After all, I did say nobody was ever able to copy them, and their brain is to these days the only thing that can use their ability.

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Author's note: this story was meant to be creepier than the others. The idea came out when I read the first novel (the only one I read until now), where it's explained that Touma's Imagine Breaker was not detected by System Scan because the boy required to use his hand on an ability in order for Imagine Breaker to work, but the machine had no ability.

Now, that is a weird explanation and I assume I'm going to find a different explanation later in the novel series (pls don't spoil when you post a comment), because if that was the reason, then a load of abilities would remain undiscovered, like AIM stalker, which requires another esper to activate. This led me to picture Ability Scanner, an ability that could detect other abilities. Touma's power would still be undetected, because even Ability Scanner would be cancelled by Imagine Breaker, but at least they could finally find all other abilities.

Apart from all that, I think the ending already implies this strongly enough, but just to make sure: yes, the idea is that Academy City kills Ability Scanner users to harvest the part of their brain that actually contains the ability, in order to insert that in System Scan machines around the various facilities.