Acqua of the Back Arc

The Acqua of the Back Arc is a major story arc of Toaru Majutsu no Index. It features a second invasion on Academy City lead by God's Right Seat member Acqua of the Back, who is after Kamijou Touma's right hand. At Touma's side are Itsuwa and the rest of the Amakusa Church and later, Kanzaki Kaori. It’s the first arc to feature a Saint vs Saint battle, the first physical appearance of God’s Right Seat leader, Fiamma of the Right, and the fate of Vento of the Front after her failed invasion on Academy City.