Toaru Majutsu no Index is set in a city of scientifically advanced superhuman students, but in a world where magic is also real. Toma Kamijo's right hand, the Imagine Breaker, will negate all magic, psychic, or divine powers, as well as his own luck. One day he finds a young girl hanging on his balcony railing named Index. She turns out to be a nun from the Church of England, and her mind has been implanted with the Index Librorum Prohibitorum-all the magical texts the Church has removed from circulation. His encounter with her leads him to meet others from the secret world of science and magic and an adventure with his friends where science and magic collide. Toma's unusual power places him at the center of conflicts relating magicians and science-based espers in Academy City. As Toma tries to help and protect his friends, he learns the people he knows are not as they appear and begins to attract the attention of magicians and espers alike as they try to unravel the secrets of Academy City and Index.
The side-story, Toaru Kagaku no Railgun, focuses on Mikoto Misaka, one of the seven Level 5 espers in Academy City, who has control over electricity. Along with her friends, she investigates a phenomenon known as the Level Upper, which boosts an esper's power, but causes them to fall into a coma soon after using it. Afterwards, she learns about the 'Sisters' experiment, in which clones of her are mass-produced for the purpose of raising the level of another esper, which ties into the third light novel.
This story has the part which was created by referencing Wikipedia, so the licence of GFDL is applied to this story.