The Book of Law is an encrypted grimoire that only one nun has the skills to decipher—and it’s gone missing! If its magic is ever used, it will bring about all sorts of ruin. Now, the church just has to keep the gifted nun safe. How hard can that be?

The battle over Orsola, the only nun who can read the Book of Law, continues as Toma is forced to act as an unwitting decoy. The Amakusa clash with church representatives, but the real culprit behind the plot might not be who Toma expected.

With Orsola taken hostage, Toma and his gang take the battle to the church. There, Index unleashes a mighty spell. Things look bleak for the Roman Orthodox, but their willingness to sacrifice themselves might just give them the upper hand.

The Roman Orthodox nuns continue their attack as Orsola risks everything to have Index decipher the Book of Law. The infamous grimoire could help them finally defeat their enemies—but that’s only if it works like it's supposed to.

After winning a trip to Italy, Toma and Index run across a few old acquaintances. But wherever these two go, disaster is sure to follow—this time in the form of assassins!

Agnese makes a deal with Toma and Orsola that guarantees their safe escape from the Roman Orthodox ship—so long as they take Sisters Angelene and Lucia with them. As they search for the nuns, they uncover more about the ship’s terrible true purpose.

Toma goes head-to-head with Bishop Biagio during an attempt to rescue Agnese. As the battle rages, the Queen of the Adriatic Sea is revealed to be a ship that can completely destroy Academy City.

Tōma is parachuted into a river and almost drowns but is saved by Itsuwa of the Amakusa Catholics. He explains to Itsuwa that he and Tsuchimikado are trying to find Constantine's Document, also known as the C Document, a magical item that was long ago given by Emperor Constantine to the Pope which allowed whatever the user believes, the people living on Papal Lands also believed it, which Tsuchimikado believes is responsible for the world wide anti-Academy City protest. Bringing him to a cafe, Itsuwa explains the C Document is in Avignon and not in Rome due to the events of the Avignon Papacy and the city's ley lines allows the document to spreads it's magic throughout Europe. However, Tōma and Itsuwa are forced to abandon the cafe after rioters reazlies Tōma is from Academy City. Meanwhile in London, Stiyl and Agnese interrogate Lidvia and Biagio over information on who God's Right Seat are and their goals which Lidvia reveals they are four special individuals who sacrificed their ability to use normal magic in exchange for divine powers so they can rid themselves of Original Sin and become closer with God. As they avoid the rioters, Tōma and Itsuwa gets a call from Tsuchimikado that they need to find one of the city's ley lines so Tōma's Imagine Breaker can destroy the effects of the C Document. Just before Tōma and Itsuwa disrupts one of the site of the ley lines, they are attacked by God's Right Seat, Terra of the Left.

After being escorted to London, Kamijo and Index have an audience with the queen and three princesses to discuss the threats facing Britain. Upon dividing into separate teams, Kamijo assists with tracking down the members of New Light.

As the coup continues, even the sisters of the puritan church are targeted, while the queen and princesses find their lives in danger. Index analyzes the evidence of the Eurotunnel blast. Knight Leader is confronted by a former colleague.

Acqua and Knight Leader continue their fateful showdown in the forest. Princess Carissa reveals a devastating new technique using Curtana Original. When Kamijo and Index's lives are endangered, an unexpected ally comes to their rescue.