Set in Academy City, a city of scientifically advanced superhuman students, located to the west of Tokyo, in a world where magic is also real. Kamijou Touma's right hand, the Imagine Breaker, can negate all magic, psychic, or divine powers, but not his own bad luck. One day he finds a young girl, Index, hanging on his balcony railing. 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 leads him to meet others from the secret world of science and magic and right into an adventure where science and magic collide.

Touma's unusual power then places him at the centre of conflicts relating magicians and science-based espers in Academy City. As Touma tries to help and protect his friends, he learns the people he knows are not quite what they appear to be. To make thinks worse he begins to attract the unwanted attention of powerful magicians and espers alike, as they try to unravel the secrets of Academy City and Index.

[Source: AniDB]

A series of shorts featuring Index-tan.

When science and sorcery clash, the result is explosive in this sequel to A Certain Magical Index from the studio that brought you Shakugan no Shana!

The Book of the Law—an encoded grimoire containing catastrophic magic—has been stolen, so naturally Kamijo, Index, and a few familiar faces join in the crusade to protect the one nun who can decipher the powerful text. But as the group battles church sects and holy assassins, they realize that discovering who their true enemy is may be more difficult than saving the sister. Meanwhile, an organization known as the Science Society resurrects an esper-producing program, a school festival brings out the competition—and drama—in the student population, and a mysterious figure negotiates the purchase of a sacred relic that could threaten the future of Academy City.

[Source: Funimation]

New series of shorts featuring Index-tan.

In the movie's story, just before the completion of the Academy City space elevator "Endymion", the main characters Kamijou and Index encounter a level 0 girl named Arisa. The Magicians are after Arisa, and they attack Academy City. A female leader named Shattoaura leads a unit from Academy City against the attack. Kamijou and Index learn from Stiyl that Arisa is key to a brewing war between the sides of Magic and Science.

[Source: Anime News Network]

Bonus animation featuring Index-tan included with the BD special edition of the Toaru Majutsu no Index: Endymion no Kiseki movie.

Science, magic, and a nun on the run! Kamijo and Index return just in time to celebrate A Certain Magical Index’s 10th anniversary with a brand-new season. After their deadly struggle against the Catholic Church and the pending war between magic and science, Kamijo must work harder to protect Index. But with tensions high all around, what new adventures await them in this next chapter?

[Source: FUNimation]