FIVE Over

FIVE_Over (ファイブオーバー) is a series of experiments and technologies formed by Academy City to replicate and exceed, hence the name, the powers of the 7 Level 5s. Its principles are based off macro engineering technology instead of micro quantum mechanics, Personal Reality, which gives birth to an esper's powers.

Appearance
The FIVE_Over Modelcase_"RAILGUN" powered suit is the most well-known example of the technology. Its appearance is described to be like a five-meter-long praying mantis. It has two arms, two legs, and two sickles that can fold if needed to help it stand up. Translucent wings spread out from the armor. A large cylinder-like thing used to store lots of cannons rests on its back. There is also a shield on the front side of each of its front legs, with an artificial weapon placed between those shields.

Abilities
With its name referring to the third strongest of Academy City, its main weapon is a gatling railgun. It’s an armored suit with the replicated power of the third Level 5, and is completely based on the philosophy of "using only technology to create one that exceeds the original". FIVE_Over can use its wings to move so fast that it can leave afterimages.

The Powered Suit, can operate without any person inside to control it. It can fly, though could only sweep over ground enemies from above like an attack helicopter, as they were not intended to be used to shoot down multi-purpose fighters flying at supersonic speeds at high altitude. Most importantly, they were created into target objects on the surface.

According to the author, the FIVE_Over has a lot more powerful gun than Mikoto, but if the two were to fight, Mikoto would win due to application. However, the author also states that this outcome isn’t absolute, because science and technology will continue to advance.

Mental Out
Although it is unknown as to what extent the experiment has progressed, according to Kihara Ransuu there have been experiments to create chemicals secreted in the brain and scatter them on mold to replicate the illusionary powers of Shokuhou Misaki the 5th Level 5, and is how he based his mold-induced illusions. Chemicals such as the Red Fury 03 and Blue Fear 07 have been used for the replication.

Freshmen Arc
Kuroyoru Umidori has the dying Silvercross Alpha placed in it in order to dispatch and automatically pilot the power suit ; thanks to this, the FIVE_Over's performance becomes greater than a simple AI-controlled suit. It later pursues Hamazura Shiage, Hattori Hanzou, Kuruwa, and Fremea Seivelun into a building in a coordination attack with other suits from Silvercross's collection.

After creating an elaborate trap and using various objects, Shiage and the others manage to take down the FIVE_Over by damaging the suit to the point where its AI no longer becomes functional. When Kuroyoru attempts to kill Accelerator with thousands of artificial arms, the hijacked FIVE_Over fires at her and destroys practically all of her equipment; Shiage had removed and replaced its control system with the Dragon Rider's suit, which allows him control of the FIVE_Over.

Baggage City Arc
Hints of another FIVE_Over being under development is referenced during this arc, most specifically, Shokuhou Misaki's powers.

During Academy City's suppression of Baggage City, unmanned variations of the Modelcase_"RAILGUN" is deployed en masse and are used as the main ground units against Science Guardian’s unmanned powered suits and tanks. With the HsB-07, they show the technological superiority of Academy City. Kamijou Touma later mentions seeing the remains of a few Modelcase_"RAILGUN"s when he was there.

Magic God Othinus Arc
After Touma finished his negotiations with Roberto Katze about what to do with Othinus, several tanks used by the Danish military as part of their diversionary forces for Operation Norse Wind are enveloped in an explosion. After getting his bearings again, he sees the cause of the explosion was of an incoming fleet of around 150 FIVE_Over Modelcase_"RAILGUN"s. The unmanned FIVE_Overs then begins a biometric scan for Othinus and Kamijou Touma with instructions to eliminate any and all interference while broadcasting a message of their intentions to those in the surrounding area via speakers from the remaining tanks. As the fleet begins to close in on the fleeing duo the system for the FIVE_Overs is suddenly hacked and had their preparations for the firing sequence interrupted. As a result FIVE_Overs begin falling out of the sky and even crashing into one another, as the area clears up Touma notices that all of the FIVE_Overs covering the snowy plain all had their heads tilted focusing on one fellow machine in particular, the reason for this is revealed to be Misaka Mikoto riding atop the central FIVE_Over, now under her control.

Touma then proceeds to release the FIVE_Overs from her control one by one using the Imagine Breaker forcing her to deal with the now rampant machines. Because of this action not only is she forced to destroy the FIVE_Overs, but machines that might have been freed and ones that might have been in the confusion of the battle dealing with the others as well. Touma, having disappeared in the confusion, reappears on the back of an offline unit she is standing on in order to fight her. After the fight, Mikoto stays behind to hold off the remaining FIVE_Overs that would eventually escape from the control of her hacking.