It’s the Daihasei Festival, and everyone’s parents are in town! As Toma and Mikoto compete against each other in various events, a Roman Orthodox magician and her assistant negotiate to purchase a powerful relic from the English Puritan Church.

With the Shorthand cancelled, Stiyl uses his magic to locate Oriana, causing a fight to erupt. In London, Laura learns that Oriana’s deal might not be for the Stab Sword, but for something else entirely.

Tsuchimikado’s location spell backfires and leads Oriana straight to him, resulting an epic showdown. But he’s not the only one exposed to Oriana’s magic: Himegami feels the force of the spell caster’s power, and may not survive.

Toma and Tsuchimikado investigate the history of a sacred artifact as they try to figure out what Oriana’s plan is. When they discover they have only until nightfall to stop her from enacting an evil plot, the battle for the future of Academy City begins!

As Toma and the others come close to beating Oriana, the motivations behind her actions are finally revealed. But taking out Oriana might not be enough to stop her plot from reaching a catastrophic completion!

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.

Tsuchimikado appears and joins forces with Tōma and Itsuwa against Terra, who flees when a platoon of powered suits sent by Academy City interfere with their fight. Tsuchimikado then stays behind to stop the suits while Tōma and Itsuwa chase after Terra at the Palais des Papes. Once there, Tōma contacts Mikoto by phone and learns from her that according to the media, Academy City launched an attack on Avignon in retaliation against a plan to attack it, but their conversation is cut short when Terra, having the C Document in his hands, attacks him. During their fight, Terra realizes that Tōma still has not attained the full power of Imagine Breaker because he lost his memory, but nevertheless, Tōma takes advantage of a weakness in Terra's abilities to defeat him and destroy the C Document. Just as Tōma is about to inquire Terra about what he knows about Imagine Breaker, a squad of stealth bombers led by Accelerator attack the palace, allowing Terra to escape. However, at St. Peter's Basilica, Terra is killed for involving civilians in the conflict by Acqua of the Back who decides to take the war against Academy City personally after Terra and Vento's failures.