"A Certain Magical Index" is a Japanese light novel series written by Kazuma Kamachi. It is set in a world where science and magic coexist, focusing on a city called Academy City, which is known for its advanced scientific research and development of esper abilities. The story follows a young boy named Touma Kamijou, who possesses a unique power called Imagine Breaker, allowing him to negate supernatural abilities. The plot centers around Index, a young girl who is a living library of magical texts. She becomes entangled with Touma as various factions, including magicians and espers, seek her for their own purposes. The series explores themes of friendship, conflict, and the balance between science and magic.