Toaru Majutsu no Index Light Novel Volume 16 was first published on June 10, 2008. It continues Touma's struggle against the Roman Catholic-based group God's Right Seat, and finally features an opponent that he can't even stand against. Aside from the main story, this volume also presents the story of its main antagonist Acqua of the Back in "Between the lines."
Acqua of the Back of the dark side of the Roman Catholic Church, "God's Right Seat", has finally made his move. With the powers of a Saint and the special gift granted to members of the "God's Right Seat" in his possession, the strongest and worst enemy of Kamijou Touma's "right hand" aims to infiltrate Acadmy City.
With Acqua a clear threat to Kamijou Touma's life, the Anglican Church puts Touma under the watchful guard of the Amakusa-Style Remix of Church's Itsuwa. Because of this, Itsuwa stays overnight with Touma, and with her outstanding culinary skill drags along the freeloader nun Index into their stay. And, from Kamijou Touma's eyes flows a trickle of tears...
However, at that brief moment of rest comes their strongest and greatest opponent...!
- Prologue: The Standing of a Leader — Stage_in_Roma.
- Chapter 1: From Peace to Ruin on the Proceeding Path — Battle_of_Collapse.
- Chapter 2: The People Who Stood Up From Defeat — Flere210.
- Chapter 3: The Duel to the Death Between Entirely Different Monsters — Saint_VS_Saint.
- Chapter 4: Who is Protected By Whom? — Leader_is_All_Members.
- Epilogue: The Guide to Even More Mayhem — True_Target_is••••••