While Kazari takes a lost Last Order home, Accelerator arrives at his location and faces Saraku, a teleporter of MEMBER and defeats him after realizing Saraku can only teleport behind his opponents. Elsewhere, MEMBER's leader "The Professor" confronts Teitoku only to be killed by the latter after using his power, Dark Matter. Meanwhile, BLOCK starts their real goal, to shut down the city's surveillance system and help 5000 mercenaries invade the city. However, one of their members is actually Etzali in disguise, who alerts the city's drone helicopters to head to their location and stop the mercenaries. Despite their heavy loses, the remaining BLOCK members, Saku Tatsuhiko and Megumi Teshio, continues their next part of the plan, bringing the mercenaries to Academy City's detention facility and kidnap Awaki's gang to use as leverage to make her help them enter the Windowless building and kill Aleister. GROUP heads to the detention facility where Accelerator stays back to hold off the remaining mercenaries while Etzali faces off against Xochitl, a MEMBER agent and his colleague from the Aztec organization who has come to Academy City to kill Etzali for treason. Tsuchimikado and Awaki confronts Saku and Megumi trying to free Awaki's gang but Megumi kills Saku for endangering the hostages and decides to forcefully get the information from Awaki instead. Despite Megumi knocking out Tsuchimikado, Awaki is able to defeat Megumi after getting over her trauma of teleporting herself. With the hostages safe and Etzali saving Xochitl's life from the grimoire she was using, GROUP heads back home. However, Teitoku arrives at ITEM's apartment after torturing Frenda for information.

Hamazura desperately tries to rescue Takitsubo when the building she is in falls under terrorist attack. Stephanie hunts down Kinuhata to exact revenge for Sunazara. Accelerator seeks out assistance from an unlikely benefactor.

While Hamazura is out running errands for Mugino, SCHOOL stages an attack on ITEM. When Mugino runs from Kakine, Takitsubo offers to protect Hamazura, but ends up needing his help instead. Kakine issues a challenge to Accelerator.

Accelerator attempts to make amends for his past by doing a few good deeds, but ends up attacked by a group led by someone from his past. Meanwhile, Toma discovers strange goings-ons in the police force and overhears talk of an intruder in Academy City.

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.

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.

Accelerator and the other members of GROUP are assigned to eliminate the members of Spark Signal, a terrorist group which has taken hostages. Hamazura and Kinuhata find themselves on the run when they defy the city's higher-ups.

Kamijo tangles with Stiyl, upset with the magician’s rough behavior toward Index. When quick thinking allows Kamijo and Index to escape, they head to the one person that might be able to help them.

Mikoto convinces Toma to sign up for a couples cell phone contract with her so she can get an adorable promotional item—but how far are the two willing to take the ruse before they get, well, maybe a little too close.

When Accelerator deduces who is pulling all the strings in Academy City, no person—or building—is safe from his rage. Meanwhile, Toma goes on a mad dash through the city looking for Last Order, but what he finds is an angel.

In order to save Last Order, will Accelerator sacrifice himself? Vento’s past is revealed, Toma delivers a very Toma speech, and Index sings a song as the battle rages on in Academy City.

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.

Team GROUP captures a blackmarketter for questioning who is later killed by an esper wearing a steel helmet. Etzali investigates the blackmarketter's home but a black ops team arrives. Etzali disguises himself as one of the operators but not before leaving some clues to his team. GROUP learns the blackmarketter sold a weapon to a sniper named Sunazara whose target is Monaka and Accelerator stops the assassination attempt after Awaki teleport him to Monaka's location. GROUP soon learns the assassination attempt was a distraction for another darkside team named SCHOOL, lead by the 2nd Level 5, Teitoku Kakine, and their real target was the particle engineering laboratory. To further complicate matters, the other teams like MEMBER, BLOCK and ITEM are getting involved as well. Meanwhile, the former Skill-Out Shiage is now working with Team ITEM, led by the 4th Level 5, Shizuri Mugino and her teammates, Rikō Takitsubo, Saiai Kinuhata and Frenda Seivelun, who treat Shiage with no respect. Learning about Monaka's assassination attempt, ITEM reazlies SCHOOL's real goal and heads to the particle engineering laboratory only to fight with the steel helmet esper. Despite killing the esper, Teitoku escapes with the device he stole, forcing ITEM to split up while Shiage runs away from SCHOOL's Pink dressed Assassin. Elsewhere, GROUP learns Team BLOCK is planning to steal Biological weapons from the city's virus vault but Etzali reveals the vault is a decoy as their real target is Satellite control center which controls the Hikoboshi 2 orbital laser weapon in space. Accelerator heads to the Satellite control center alone to fool BLOCK that they are falling for their trick.

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.

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.

Técpatl and Unabara square off in Shiokishi's chambers, while Accelerator and Sugitani face each other in the hallway outside. Kinuhata discovers the true reason for the current assault against herself, Takitsubo, and Hamazura.

After dealing with the sorcerers at the Russian airbase, Accelerator has a Misaka clone skydive down to confront him. Vento challenges Fiamma while Kamijo and the others watch on. Hamazura gets some disturbing news from Digurv.

Kamijo runs into Sasha Kruezhev, and he continues to formulate a plan to stop Fiamma. Hamazura and Takitsubo discover an imminent threat to Digurv's village. The archangel Gabriel rains havoc upon the Russian and Academy City forces.

While Komoe helps Index in healing her wounds using magic, Toma meets Stiyl's partner, Kaori Kanzaki and learns from her why they are hunting Index and the organization, Necessarius, The Church of Necessary Evil.

Touma tries desperately to save Index's memories before it is too late.

Following the events of last episode and the activation of Index's defense mechanism Touma struggles to hide his amnesia from Index.

Mikoto’s clones use their telepathic network to enlist Misaka 10032 to aid them in stopping Musujime from rebuilding the Tree Diagram in an effort to find out why humans are the only beings with esper powers.

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.