Toaru Majutsu no Index Light Novel Volume 08/Prologue

Synopsis
At Tokiwadai Middle School, the students are undergoing ability testing. Shirai Kuroko, a Level 4 teleporter, is getting her range and accuracy evaluated on what looks like a shot putting field, along with other 'projectile' type espers. She teleports a sandbag 78 meters, but due to that distance being near her limit of control, misses the target by 54 cm. While complaining about the weather hurting her concentration, she is approached by Kongou Mitsuko, a Level 4 wind esper. Kongou insults Shirai for getting overemotional about her test scores, saying that her own power is better. Hoping to impress Shirai, she proposes for Shirai to join her in a 'faction.'

These factions act like clubs, where students with similar interests can gather to help each other develop their powers. They also use their combined powers to influence and gain connections outside of the school. Kongou is confident in her own powers, and hopes to use them to attract strong followers to her side. However, Shirai turns her down. Even with Kongou's not inconsiderable powers and her family's influence, she argues, a faction could still be easily taken down by other factions.

At this point, an explosion in the swimming pool frightens Kongou. Shirai explains that the explosion was caused by Misaka Mikoto, the Level 5 'Ace of Tokiwadai.' Implying that she already has connections with strong people, she says that if Kongou were to start a faction simply for her own pride, Misaka would come and stop her.