A certain unlikely hero...No one was able to stop Second Princess Carissa's plot in time, so the worst has come to pass: London has fallen. The city of magic, home to the English Puritan Church and Index, now rests in the hands of the Knight faction. Soldiers control nearly every critical part of the country, commandeering the very streets of the capital. Still, the Puritan sorcerers haven't given up the fight just yet!As the battle for the UK rages on, Touma heads to Folkestone to save Index-only to run straight into the coup d'état's mastermind herself! Worse, Acqua is still alive, and his holy sword, Ascalon, is pointing not at Touma but at Carissa!

The latest clash of magic and science in Academy City is leaving bodies strewn across the streets! As Accelerator takes on Amata Kihara and the secret ops team known as Hound Dog, an intruder from the Roman Orthodox Church-Vento of the Front-infiltrates the city to crush Touma and his Imagine Breaker. With Touma and Accelerator fighting for their lives, will their paths converge and turn old enemies into erstwhile allies?

Touma Kamijou just can't catch a break. He might live in Academy City, a place full of more super powered students than you can shake a stick at, but his only superpower is his supernatural lack of luck. He wants nothing more than to keep a low profile, but when a girl named Index comes into his life, it gets more complicated and dangerous than ever!

Item’s battle comes to a head as their hideout is raided, and the team reaches its breaking point. Disgusted with Mugino’s disregard for the other members’ lives, Hamazura finds the resolve to stand up to her. Mugino may be a Level Five, one of the strongest espers in Academy City, but she’ll see that even a powerless Level Zero like Hamazura can put up a fight when his back is against the wall!

After a tense verbal standoff, Liselotte Cretia of the Galarc Kingdom is abducted by the sixth hero, the self-proclaimed Saint Erica. With the king's permission, Rio sets off to save her--with the help of her head attendant, Aria. Meanwhile, while in captivity, Liselotte witnesses the current state of the remote nation of the Holy Democratic Republic of Erica with her own eyes. Just who is Saint Erica trying to get revenge on?

Touma Kamijou's life is one of perpetual misfortune, which is why no one is more surprised by his sudden stroke of luck than Touma himself! Having won a trip for two to Venice, the City of Water, Touma and Index are excited for a European excursion. But the Italian peninsula is the home of the Roman Orthodox Church, and when old friends and foes alike show up, Touma's hopes for a relaxing getaway might just get washed away!

Touma has been called out by Mikoto to fulfill his punishment, but can anyone call taking pictures together and getting matching cell phone straps "punishment"...? The arrival of Mikoto's "little sisters" makes their "battle" even more fraught!

The horrifying experiment to make Accelerator into an all-powerful Level Six has commenced--and it involves the wholesale slaughter of the little sisters cloned from Mikoto Misaka. Can Touma find a way to stop the seemingly invincible Accelerator? Could it be that weakness is stronger than strength could ever be?