A Certain Magical Index, Vol. 16 (light novel)

A certain unlikely hero...Acqua of the Back, agent of the Roman Orthodox Church, has finallymade his move. The incredibly powerful saint and member of God's Right Seat is on the hunt for one thing: Touma Kamijou's right hand!
After receiving a warning letter from Acqua, the English Puritan Church dispatches Itsuwa to serve as Touma's bodyguard. But for some reason, the first thing she does after arriving in Academy City is show off her incredible cooking and housekeeping skills. It's enough to bring tears to Touma's eyes, but the freeloading Index only perceives a threat to her position...
The comfortable serenity is soon interrupted, though, when their worst enemy appears on the scene...!

Kazuma Kamachi is a Japanese light novel author and creator of the massively popular series, A Certain Magical Index, its sequel, A Certain Magical Index: New Testament, and a manga adaptation, as well as two spin-off manga series, A Certain Scientific Railgun and A Certain Scientific Accelerator.