Level 5

Level 5 is currently the highest esper level to be accomplished in Academy City. Only seven out of the 2.3 million students currently participating in the Power Curriculum Program have officially achieved this rank, indicating the immense level of difficulty involved in reaching it.

Abilities
Level 5s are espers who hold tremendous amounts of supernatural power, their talents far exceeding that of other espers.

They can be somewhat divided between those having unique abilities (also referred to as Only Ones), and those who possess the ultimate version of a common sort of power (also referred to as High Ends), such as Telepathy and Electromaster.

Some of the most powerful Level 5s are among the few espers capable of using their abilities to exert control on the planetary environment or largescale climate, with Accelerator's vector control and Misaka Mikoto's high-voltage electricity capable of doing this.

Personality
A particular object of notability of all the Level 5 espers is a recurring instance of mental instability, be it comedic or serious. Mikoto, the first Level 5 seen in the series, has a comedic obsession with defeating Kamijou Touma, although she has been referred to as the sanest one out of all the Level 5s.

Sogiita Gunha believes himself to be an ally of justice and purposely acts in accordance of superheroes in fiction. Accelerator, Kakine Teitoku, Mugino Shizuri, and Shokuhou Misaki all demonstrate more sociopathic or psychopathic tendencies with the willingness to hurt people on a whim, though this may be more related to their background more than anything else. However, both Accelerator and Mugino have become less violent lately because they feel guilty about all the harm they've done. Misaki has also demonstrated that she does care about her friends and is willing to go out of her way to save them.

Due to this, only Mikoto is the one apparently competent enough to be used as a marketing mascot or demonstrator for Academy City. Even then, it is not unheard of for any of the Level 5s to be requested for demonstration.

That said, the essay The Wall Between Level 3 and Level 4 from Toaru Majutsu no Index no Subete seems to reject this premise, stating that gaining high level powers like Accelerator and Mikoto did is the result of having strong minds and firm ideologies and principles.

In addition to this, many of the Level 5s are not on good terms with each other, although they would still sometimes form alliances if the situation called for it.

Circumstances in Academy City
Because the Power Curriculum Program is part of Academy City's curriculum, the strongest of its espers are most likely to be honor students. This is exemplified by both Mikoto, who is one of the top students of Tokiwadai Middle, and Accelerator.

Due to the immense power of the Level 5s' abilities, their primary applications are banned in the Daihaseisai.

Most of the currently known Level 5 espers have been attributed a nickname that is either the name of their esper ability or related to it. Currently, Accelerator is known solely by his nickname.

Promotion and Ranking
Promotion to Level 5 is approved by the Academy City Board of Directors.

The ranking of the Level 5s is dependent on the worth of their abilities to the ongoing researches rather than based on the relative strength of their power. It is unknown what the initial rankings were and how they got their current ranks: the only known cases are Misaka Mikoto and Shokuhou Misaki, both becoming Level 5s soon after reaching middle-school. Shokuhou was initially of a higher ranking than Mikoto, who was the lowest-ranked at the time, before she surpassed her a few months after the two entered Tokiwadai, with the two having acquired their current ranks by August of that year.

Research and Countermeasures
Level 5 espers have specialized research facilities that are dedicated to them; for example, Accelerator being part of the Special Ability Institute, Dark May Project, and many more. Most Level 5s participated in or were subjected to inhumane experiments. Misaka Mikoto however is one Level 5 not associated with any research institute, partly due to her own effort and partly due to complementary education of Tokiwadai Middle, which possesses its own subsidiary facility for Level 5s. Level 5s most likely get paid with the most money amongst their other esper peers as part of the curriculum's payment program for the espers as being part of the experiment.

Because of their overwhelming power and the fact that their developing minds can make them act based on emotions rather than logic, the higher-ups of Academy City view Level 5 espers as a potential threat. To rest easy they created Rensa, a cyborg that can use the abilities of the #1 up to #6 in order to deal with them in the case they decide to go against the city, supposedly capable of defeating all seven of them. Other, more specialized, individual countermeasures have also conceived and developed by various parties.

The Five Overs are a series of experiments and technologies developed to replicate and exceed, hence the name, the power of the seven Level 5s, with principles based on macro engineering technology rather than micro quantum mechanics that produce esper abilities. Besides the main series, which uses similar methods as the original ability to reproduce their power, there is also the Five Over Outsider sub-series which uses methods different from the original ability to reproduce the phenomena, resembling the original esper power rather than closely replicating it.

Other creations have been made based on research of the Level 5 abilities and incorporate their principles, with some directly incorporating the abilities themselves (e.g. Exterior being a giant brain grown from a cultivated cerebral cortex sample to use Mental Out, Equ.DarkMatter and Sample Shoggoth being created from and utilizing Dark Matter etc).

Previous Generations
Although there are seven officially recognized Level 5 espers in Academy City in the present day, there have been other Level 5s in the past.

Of note, the first modern esper, the Beginning Child, was developed before the current Level system was implemented, officially "disappearing" but being secretly frozen as she couldn't be controlled with the technology of the time. On witnessing her ability after her revival, including her manipulation of climatic weather conditions as part of her environmental modification and localized terraforming, Kamijou Touma and Kumokawa Seria speculated that she would be classed as Level 5 if ranked on the current system.

A Level 5 (who claimed to be the former #1) of the mysterious and rarely mentioned "previous generation" before the current one,   and "past" at least one year before the main story (given a conversation between Kamijou Touma and Shokuhou Misaki), left behind a legacy in the form of two Relics, which manifested their will and power, their ability to manifest Shadow Metal and control a special territory created by enveloping space and filling it with nanometal particles, heralded by a chill in the affected area. These Relics were connected to events occurring around the same time as Shokuhou Misaki's participation in Tokiwadai's student council presidential election,    with a group connected to that generation and symbolized by two squares (cubes) on the move (seeking both the Relics and cubic crystals of Shadow Metal),  and the influence of the Relics themselves being exerted through several individuals. Besides the Relic wielders,   one of the election candidates, Kamino, had square-shaped eyes and used a spatial control ability affecting a cube-shaped area, the usage of which provoked a feeling that reminded Shokuhou of the past Level 5,  though any exact connection is currently unknown.

Other
On the magic side, Saints have rankings akin to the Level 5s, based on their level of contribution to society.

Trivia

 * When discussing the existence of Anna Sprengel with Kamijou Touma and Accelerator, Aleister Crowley uses the term "#0 Level 5" as comparison, showing the mystique and persuasive ability of "a missing superior rank". As it was only an example, it is unknown if the 0th Level 5 exists even after Anna Sprengel was proven to be real.
 * At the time of this analogy, the existence of the Beginning Child, the first modern esper developed before the present-day ranking system and speculated to qualify for Level 5 under the current scale, had not been revealed.
 * The light novel volumes and manga chapters in which each of the seven Level 5s debuted are as follows:

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