Orsola Aquinas Rescue Arc

The Orsola Aquinas Rescue Arc is a major story arc in Toaru Majutsu no Index storyline. It focuses on the rescue of the title character of the arc, Orsola Aquinas, a member of the Roman Catholic Church who has found a way to decipher the mysterious Book of the Law, a grimoire that is said to hold great power. The arc marks the first time Touma battle against the Roman Catholic Church, as well as the first as the first time two different Christian sects – Anglican Church (specifically Necessarius) and the Roman Catholic Church (specifically Agnese Forces) – come into conflict.

Political Strife in the Magic Side
After the destruction of one of the Roman Catholic Church's holy artifacts, the Gregorian Chant, during the Deep Blood Arc, the church's power has been weakend considerably, enough for them to have a power struggle within their own ranks. As the Roman Catholic Church is still the largest and most powerful Christian sect in the world, and desired to maintain it's dominance; because of this, after discovering that Orsola Aquinas can decipher the Book of the Law, a powerful grimoire that is said to end the age of the religion based on the cross (Christianity), they created an elaborate plan to capture her (and later execute her in secrecy), by fabricating the story that the Book of the Law that was being transported by Japan for exhibition and was stolen by the Amakusa Catholics, and also kidnapped Orsola Aquinas. The Roman Catholics sent out one of their main fighting strengths, Agnese Forces, which consists of 250 battle nuns, to execute the mission.

The Anglican Church however, was allowed to aid the Roman Catholic Church's in their effort to capture her Orsola Aquinas, at the insistence of Archbishop Laura Stuart. Kanzaki Kaori, a Saint and a member of Necessarius, has recently went missing during the incident, and is presumed that she will act on her own accord in order to aid her former comrades, the Amakusa Catholics, as such problems will definitely arise if a Saint would intervene. Laura Stuart sends out Stiyl Magnus to retrieve Index and her guardian, Kamijou Touma to aid with the mission of rescuing Orsola Aquinas with the Roman Catholic Forces. Laura also instructs Stiyl to give a crucifix to Orsola Aquinas when the opportunity arises.

Orsola Aquinas

 * Main article: Orsola Aquinas

Orsola Aquinas is a Roman Catholic Church nun, who is famed for spreading the word of the gospel in three pagan countries and has a church named after her. She has been reported to have found a way to decipher the Book of the Law, using incomplete copies of the book. The reason being, is that she wants to find a way to destroy grimoires as she sees that nothing good can truly be gained from the power of grimoires.

Because of her capability of deciphering the Book of the Law, Orsola was targetted by the Roman Catholic Church, and was forced to seek the protection of the Amakusa Catholics.

Kanzaki Kaori

 * Main article: Kanzaki Kaori

After hearing of the reports of the Roman Catholic Church, that the Amakusa Catholics have stolen the Book of the Law and kidnapped Orsola Aquinas. Kaori returns to Japan, to observe if the church she has left long ago, has truly wavered from the path that she guided them on when she was still their leader.

Other Factions
Meanwhile, several members of the Knights of England swam from England all the way to Japan, in an effort to solve the situation on their own due to political turmoil between the Knights and the Church, by disobeying the orders of Laura Stuart to assist the retrieval of Orsola Aquinas and the Book of the Law and instead simply kill all the Amakusa Catholics, regardless of the relationship it has with the Church or the Roman Catholics, as it does not affect Britain. However, they are later attacked by Kanzaki Kaori and were easily decimated in a matter of seconds.

Tsuchimikado Motoharu, a operative and a spy for various organizations, was mobilized as well by an unknown faction to retrieve the Book of the Law when the Roman Catholic Church and the Amakusa Catholics are to fight.

Prelude
Before the events of the arc took place, Orsola Aquinas escaped from the Amakusa Catholics, believing that they had ulterior motives (specifically to seek the power of the Book of the Law) instead of just protecting her. She later enters Eastern Tokyo, to seek refuge in Academy City, an enemy of the Magic Side.