Document of Constantine Arc

The Document of Constantine Arc is a story arc in Toaru Majutsu no Index, and is part of the God's Right Seat Arc. It deals with the aftermath of the Roman Catholic’s invasion in Academy City, which leads to numerous pro-Catholic protests over the world, most targeting Japanese-related subjects.

The Arc focuses on Kamijou Touma, backed by Itsuwa from the Amakusa Catholics and Tsuchimikado Motoharu, trying to stop the riots, revealed to be causes by the Catholic Church itself with the magical artifact know as the C-Document (or Document of Constantine), in order to do it, Touma travels to Avignon, France, where is suspected to be the ritual site of the C-Document.

Trivia
This is the first arc anyone has learned of Touma's amnesia since the first Light Novel and story arc of the series.