Dark May Project

The Dark May Project (暗闇の五月計画) was an experiment carried out in Academy City, aimed at replicating Accelerator's powers by implementing similar patterns of ability operation.

Principles
The Dark May Project was an experiment that used subjects who were most likely Child Errors, in an effort to replicate Accelerator's powers by using a similar pattern of ability operation. This was done by referencing the cognitive patterns of Accelerator himself in order to optimize the personal realities of certain espers taking part in the experiment. Kinuhata Saiai was once a part of this experiment which taught her to use her ability as an automatic self-defense capability that activates if she is attacked, similar to Accelerator's vector shield. Kuroyoru Umidori was also a subject in the project, and apparently killed all the researchers at one point, bankrupting the project.

Saiai stated that it wasn't usual for children of the experiment to end up well, as many of them ended up in dissection tables while scientists tried to figure out in which part of the brain the personal reality was located.

One of the after effects of the project is that Accelerator's personality may be ingrained into the subject. Kuroyoru Umidori, Tsurigane Saryou, and Yuzuriha Ringo seem to be the ones to have such side effects.

Later during the events of Toaru Kagaku no Dark Matter, it was revealed that the Dark May Project in truth implanted specific portions of Accelerators thoughts, feelings and beliefs into their test subjects in the hopes of improving the ability development of its Espers. The thoughts and feelings being the first ranked's sense of Pride, Suspicion and Attachment.

After successfully implanting the Accelerator's thought patterns, the researchers would then begin brutally testing their test subjects to see if their Esper powers have gone through any changes/improvements using highly painful & brutal methods. As seen during their tests and experimentation on Yuzuriha Ringo where by using various painful stress inducing tests & drugs in order to stimulate her brain and force her esper powers to improve its "values". These painful and extremely traumatic tests in turn would then leave her being severely injured on a daily basis and her developing several gaps in her memory due to the trauma and stress. Later the researcher's were even willing to go as far as to using severe psychologically torture on Ringo in order to stimulate her implanted sense of "attachment" from Accelerator by physically abusing her friend, Ryuugou Tomoka right in front of her and chaining her to the wall to stop her from helping her in order to gather more data on her power's ability to improve when she was put under immense stress and psychological pain.

Variations
Besides the main Dark May Project involving Accelerator's thought patterns, there was at least one "variation" of the project with a similar yet different approach. Located in a separate laboratory from the main project and run by a sub-team, it was the facility which Child Errors Shundan Kimi, Tsurigane Saryou, Wanigawa Raifu and Shirakinu Honoka were given to in exchange for a loan for their financially-struggling orphanage, under the guise of a "power boosting lab". The group were screened for the main project but did not pass the primary screening phase.

The experiments at the laboratory involved tampering with specific areas of the test subjects' brains and observing the effects of the subject's abilities. This was obstensibly for boosting their abilities (with Raifu in particular going from Level 2 to 4, at noticeable cost to her mental state), but in the case of Honoka her ability was deliberately diminished.

Besides armed guards, the sub-project's facility possessed security robots known as Spriggans, programmed to capture targets.

Background
At some point in the past, Kuroyoru apparently killed all the researchers, bankrupting the project.

Battle Royale Arc
When Kakine Teitoku brought up Kinuhata Saiai being a former test subject of the Dark May Project, she mentioned that she was super happy compared to the test subjects of Produce who had their brains chopped up like a Christmas cake.

World War III Arc
The Dark May Project was mentioned during Accelerator's discussion with Misaka Worst after their arrival in the Elizalina Alliance of Independent Nations. Although Worst hadn't warmed up to him for sparing her, the Level 5 urged her to cooperate in looking for better leads related to the parchment pieces. Worst refused, but Accelerator reminded her that her fate as a clone would be the same because they would remain disposable unless something was done. The Third Season clone stubbornly remained uncooperative until Accelerator opened a possibility for her to be useful through the Dark May Project. Misaka Worst saw it a worthy opportunity and decided to agree.

Freshmen Arc
When they met, Accelerator told Kuroyoru Umidori that he had once eliminated Academy City's dark side and wanted to know why her dark organization was still active. Kuroyoru replied with anger that not everyone in the world would just get along with one another. Accelerator realized that she was a subject of the Dark May Project after observing her pattern of calculation and manner of speaking.

Jailbreaker Arc
The events surrounding the Jailbreak Trial involved the survivors of one of the project's variations, particularly Shundan Kimi with Tsurigane Saryou and Wanigawa Raifu abetting, and were heavily influenced by the events which had transpired at the lab in the past and their after-effects.

Following Tsurigane's betrayal of the Kouga, Oumi Shuri learned of her involvement in the Dark May Project and its apparent role in her transformation.

Yuzuriha Ringo Arc
Kakine saved Yuzuriha Ringo from a bunch of thugs because she was one of the survivors of the Dark May Project. Yobou Banka found out about more survivors to contact, but Kakine refused the offer so as not to be detected. His goal was not to fight with Accelerator, but he wanted to know Accelerator's calculation pattern for an unknown reason.

Another survivor of the project, Kuroyoru Umidori, was involved in the events which followed, picking a fight with Yuzuriha Ringo.

Main

 * Kinuhata Saiai
 * Kuroyoru Umidori
 * Ryuugou Tomoka (deceased)
 * Yuzuriha Ringo (deceased)

Variation

 * Shirakinu Honoka (deceased)
 * Shundan Kimi
 * Tsurigane Saryou
 * Wanigawa Raifu