Daihasei Festival Arc

The Daihasei Festival Arc refers to two major storyarcs that occur at the same time in both the Toaru Majutsu no Index and Toaru Kagaku no Railgun timelines focusing on the events of the Daihaseisai.

Below are the links for the arcs of both series:
 * Daihasei Festival Arc (Index) - focuses on the secret events during the Daihasei Festival, wherein Kamijou Touma—and the company of Necessarius magicians —deal with magicians of the Roman Catholic Church trying to take over Academy City during the festival. Mostly concentrates on the Magic side, with minute science scenes scattered around the entire arc.
 * Daihasei Festival Arc (Railgun) - focuses on the actual events of the Daihasei Festival, wherein level 5s of Academy City are asked to participate and become the spotlight of the events.