Following the disappearance of Kamisato Kakeru after Kihara Yuiitsu stole World Rejecter, Academy City has been hit by an abnormal heat wave exceeding 55 degrees, taking out the city's infrastructure. At the same time, the city has also been infested by life forms known as Elements.[Notes 1]
- Main article: Element
In order to draw out the Kamisato Faction, who had disappeared after their initial confrontation, Yuiitsu unleashed the Elements, reduced life forms which were a hybrid of science and magic. Created in the shape of animals and plants, with a reverse of the process which converts animal and plant remains into petroleum over time, and animated by a magic-based core corresponding to one of the four elements, the Elements possessed the ability to blend in with their surroundings.
After initial contact with the Elements, the Kamisato Faction performed experiments on captured subjects and determined that their activity was lowered in temperatures exceeding 40 degrees Celsius. Following this finding, Fran used her space station Bunny Grey Messenger to flood Academy City in microwaves, creating an artificial heat wave with temperatures exceeding 55 degrees Celsius.
- There are a number of dating discrepancies between volumes taking place during December. In Shinyaku Toaru Majutsu no Index Volume 16 and Shinyaku Toaru Majutsu no Index Volume 17, there are several references to the rapid onset of the heat wave and the Elements occurring on December 4th. This directly contradicts the events of Shinyaku Toaru Majutsu no Index Volume 15 and the previous two volumes. This article and the Unified Story Timeline proceed on the assumption that the references to December 4th in Volumes 16 and 17 are erroneous.
- Shinyaku Toaru Majutsu no Index Light Novel Volume 16 Prologue
- Shinyaku Toaru Majutsu no Index Light Novel Volume 16 Chapter 3 Part 6
- Shinyaku Toaru Majutsu no Index Light Novel Volume 16 Chapter 1 Part 4
- Shinyaku Toaru Majutsu no Index Light Novel Volume 16 Chapter 4