Set in a scientifically advanced world where supernatural abilities are attained through strict scientific curricula, the story follows Touma Kamijou, a high school student living in Academy City. Despite possessing the lowest possible Esper power level, Touma hides a secret weapon in his right hand: the Imagine Breaker, an anomalous ability capable of negating any magic, psychic power, or divine miracle. Touma’s quiet life shatters when he discovers Index, a young nun from the Church of England, hanging from his balcony railing. Index holds 103,000 grimoires of forbidden magical knowledge in her
photographic memory, making her a prime target for dangerous mystical organizations seeking to exploit her power. Motivated by his unwavering sense of justice, Touma chooses to protect Index, plunging headfirst into the dangerous underworld where science and magic collide.As the narrative unfolds, Academy City’s utopian facade crumbles. Touma is drawn into escalating conflicts against ruthless enemies. He faces Stiyl Magnus and Kanzaki Kaori, members of the clandestine British magical faction Necessarius, who initially claim Index must have her memories wiped annually to prevent her brain from frying, a lie Touma violently dismantles. He also battles Academy City's most powerful Level 5 Esper, Accelerator, to rescue a young clone named Misaka 10,982 from a brutal, fatal experiment designed to elevate Accelerator to an even higher level of godlike power. Throughout these harrowing ordeals, Touma’s core motivation remains fiercely protective; he risks his life repeatedly, relying solely on his wits, physical endurance, and his anti-supernatural right hand to shatter the illusions and cruel machinations of both scientists and sorcerers.The plot thickens with the revelation of Academy City's true puppet master, the enigmatic board chairman Aleister Crowley, and the looming threat of the
Roman Catholic Church. As global tensions between science factions and magic cabals reach a boiling point, Touma finds himself entangled in global conspiracies. Alongside his classmate Mikoto Misaka—an electrically powered Level 5 Esper who harbors conflicted feelings for him—Touma navigates a labyrinth of political betrayal and divine intervention. Culminating in massive scale battles that threaten the very fabric of reality, the overarching narrative explores themes of free will, redemption, and the clash between dogma and empirical progress. Ultimately, Touma stands defiant against fate itself, continuously risking everything to save those who cannot protect themselves, forever bridging the divide between two hostile worlds.