Hasekura Reiri's Clique

Hasekura Reiri's Clique (支倉冷理の派閥), also referred to as the Hasekura Clique (支倉派閥), was the third largest clique in Tokiwadai Middle School, one year prior to the main story, led by Hasekura Reiri.

Principles
The Hasekura Clique was the oldest and third-largest of Tokiwadai's 'big three' cliques (behind the Sha Clique and the Mikagami Clique respectively), one year before the main story, during Misaka Mikoto and Shokuhou Misaki's first year at Tokiwadai Middle School. It was led by third year student Hasekura Reiri and formerly the largest clique before being overtaken by the other two (supposedly without the two intending to). Around 17% of Tokiwadai's students were members of the clique.

According to Kessai Kiyoshi (a first-year member of the clique but actually related to Sha Danshan), it was a carnivorous clique, with members willing to throw others under the bus to succeed.

Background
The clique's full background isn't known, but it was the oldest of the 'big three' cliques and was previously the number one clique. However, the number of people willing to join the Mikagami Clique and put in effort to get results, in order to have Mikagami use her ability for their benefit, led them to overtake the Hasekura Clique, briefly becoming number one before being overtaken by the Sha Clique in turn.

First Year Arc
When Misaka Mikoto was promoted to Level 5, the Hasekura Clique took advantage of her previous prideful roommate moving out to insert one of their own members, first-year Kessai Kiyoshi, into the vacancy to secretly monitor her. Not long afterwards, in early May, Hasekura Reiri met Mikoto herself and had a contest with her, confirming some of her subordinates' thoughts.

During the summer, Hasekura was away from Tokiwadai for a time for a demonstration in Paris. The clique hoped to use this opportunity to get more applicants, but this was dashed when a conflict arose between them and the Mikagami Clique, secretly engineered by Sha Danshan to undermine her rivals' progress. After the initial attack on Kazan'in Tsukasa, supposedly by the ability of Enjou Kasumi whom she quarreled with earlier in the day, the Hasekura Clique fiercely denied the allegations against them by the Hasekura Clique. A further attack that injured another Mikagami Clique member led to the nearby Kessai being targeted for retaliation, though it was stopped by Misaka Mikoto and Shin'enkouji Rurikakesu.

Though Hasekura ordered her clique not to start anything until she returned, Yasutoba Suika ignored her orders and attempted to take out Mikagami Nagisa, alone after failing to get her fellow members to follow her. Ambushing Mikagami while she was walking with Sukezawa Sena and Kadosaka Rina, Yasutoba defeated the pair after the initial escape as they tried to cover for their leader, but was defeated by Mikagami herself.

After this ambush, tensions remained high, with certain members of the Mikagami Clique in favor of a counterattack against the Hasekura Clique. Walking home at night after such a meeting, Urui Aika spotted Misaka Mikoto practicing her new technique and on trying to leave, accidentally ran into a group from the Hasekura Clique. A clash of esper abilities resulted, with Mikoto intervening on the outnumbered Urui's behalf. When this initially secret help was exposed, Amano Ayane challenged Mikoto to test her power, leading to her Railgun being used in action for the first time to save the other girls from a severed wind turbine blade, an event which further overshadowed Hasekura's performance in Paris.

When Hasekura returned, she began an investigation into the clique conflict. After a chance encounter with Shokuhou Misaki, in which Hasekura ascertained Shokuhou's character (including that she would make a good clique leader, something she suggested) and that she was not the culprit, Hasekura obtained evidence with help from Mikoto and Ruri with which to form a truce with Mikagami while looking for the suspected third party responsible for the conflict. After several days without movement from the mastermind, Hasekura tried to provoke them by making it appear that Shokuhou was also aiding her, assigning her two aides to guard her and strengthen the ruse (which others in the clique believed).

After a thwarted ambush against Hasekura herself and subsequent investigation leading to the discovery of Montgolfier's involvement, the Hasekura Clique fully supported action against the apparent culprit. During the company raid, Hasekura acted separately from her clique to detect any secondary masterminds, while Mibuki Kazan was disguised as her with the clique, with Ruri accompanying them as a member of Judgment with a search warrant. When hostilities broke out, the Hasekura Clique were reinforced by Mikagami Clique and Sha Clique, and soon defeated Montgolfier's forces, while Hasekura identified and defeated their employers Antikythera on her own. Afterwards, Hasekura felt that things had been tied up a little too neatly, but did not pursue her suspicions. At the same time, the true mastermind Sha disposed of evidence and the remaining Antikythera members she had made her scapegoat.

Named Members

 * Hasekura Reiri (Leader)
 * Kessai Kiyoshi
 * Enjou Kasumi
 * Yasutoba Suika
 * Asato Kisa
 * Amano Ayane
 * Mibuki Kazan

Trivia

 * Similar to the other two cliques in the 'big three', most members of the Hasekura clique seen so far as of (with the exceptions of Mibuki Kazan and Kessai Kiyoshi, the latter secretly related to Sha Danshan) have colors of hair depicted using shades of grey in the monochrome sections of the manga, like with their leader (brown in her case).