Um livro de feitiços foi roubado e a freira que sabe descodificá-lo foi capturada. Stiyl é enviado para resolver o caso.

Kamijo vê Orsola ser raptada pelos Amakusa e vai com Stiyl e as Agnese ao esconderijo do inimigo.

Após resgatar Orsola, Kamijo é aconselhado por Tatemiya a não a entregar aos Amakusa, o que o deixa com uma decisão difícil em mãos.

Kamijo e Index veem-se encurralados depois de serem atacados. O seu destino depende da descodificação de um livro de feitiços.

Kamijo e o seu grupo são subitamente atacados durante a estadia em Itália. A responsável é Agnese, que aceita deixá-los ir em liberdade, mas... com uma condição.

Durante uma luta, o grupo acaba por ser separado e Kamijo enfrenta Biagio.

Itsuwa reveals to Tōma she has come to Academy City as his bodyguard to protect him from Acqua, who is now targeting him for ruining God's Right Seat plans. While Itsuwa's Amakusa comrades watch from afar and plan to have she and Touma to get close and be a couple, Mikoto is still dealing with the revelation of Tōma's amnesia. Tōma brings Itsuwa to his home, where Index accidentally destroys the bathroom, which Itsuwa decides to bring Tōma and Index to a spa located in 22th District's underground city. After an awkward meeting between Itsuwa, Index and Mikoto in the spa, Tōma and Itsuwa takes a walk at a park. However, Acqua appears, having defeated the rest of the Amakusas, demands Tōma hand over his right arm which contains Imagine Breaker. Tōma and Itsuwa tries to fight back but are unable to hit him due to Acqua's Saint powers. After beating Tōma to a pulp, Acqua gives him one more day before he gets his right arm while Itsuwa feels guilty for failing her mission.

With Kamijo unconscious, Itsuwa is guilt-ridden, and receives a pep talk from Tatemiya. As Orsola researches Acqua's past, the Amakusa Church members make their stand against Acqua, at which Itsuwa reveals their new secret weapon.

Kanzaki battles Acqua under Academy City, but finds herself overpowered by his might. Mikoto runs into Kamijo after he sneaks out of his hospital room. Kanzaki works with the Amakusa Church members to find a way to beat Acqua.

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.

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.

Kamijo, Kanzaki, Index, and Vilian head toward Buckingham Palace to stop Carissa. The palace is bombarded from the floating fortress Coven Compass, and others join the battle when Carissa calls in her own cruise missile strike.