A Certain Magical Index is set in a world where supernatural abilities are a reality. Individuals who possess special powers acquired via science are called Espers (超能力者, Chōnōryokusha). Those Espers who gain their abilities without the aid of special scientific instruments, whether at birth or otherwise, are referred to as Gemstones (原石, Genseki). Others, known as Sorcerers (魔術師, Majutsushi), gain their powers upon mastering the power of magic, either from obtaining knowledge from different mythologies or by using mystical artifacts, although the existence of sorcerers is a secret to the public. While Sorcerers align themselves with different beliefs, Espers are aligned with scientific institutions. This leads to a power struggle between the magic and science factions for control of the world.
