Touma Kamijou can't catch a break. After the invasion of Academy City, political tensions continue to rise as both the science and magic factions collide head on. It appears that Academy City intends to declare war against the Roman Catholic Church, consequently plunging the whole world into global warfare. Touma soon finds himself on the front lines once again, striving to protect his friends and allies.

Toaru Majutsu no Index III serves as the last installment of the original franchise as Touma, Accelerator, and the true Level 0 Shiage Hamazura continue their separate journeys, leading up to the final act of the original light novel series.

[Written by MAL Rewrite]

After moving into his new apartment, art school student Tatsuhiko Kido discovers a crack in his wall. When he peeks inside, he makes eye contact with his neighbor, Emiru Ikuno, as she masturbates. He rushes next door to clear the misunderstanding and inform her of the crack, but accidentally trips and falls over her in the process. To make matters even worse, Emiru now has photographic evidence that would plainly depict Kido as a sexual offender. Kido then learns that Emiru has a voyeurism fetish, and is blackmailed into leaving the crack as is. Unfortunately for Kido, it doesn't stop here! Emiru is also attending the same art school that he is, and he will be seeing her far more than he would like to. Emiru and Kido are set to embark on a unique friendship with wildly erotic potential.

Mio has feelings for her childhood friend Arata, but can't convey her feelings. One day, as they continue their delicate relationship, the two fight over something trivial. After letting tensions settle, Mio goes to make up with him in the pouring rain. While on her way, she gets into a traffic accident. When she regains consciousness, a mysterious and unfamiliar world appears before her eyes.

In a not-too-distant future, humanity has established a loosely organized world government with everything managed by an international AI network called Sapientia. People live peaceful lives by loyally obeying its rational decisions. However, Sapientia's lunar development project, which sends criminals and pollutants to the Moon to maintain Earth's peace, creates disparity and poverty on the Moon, sparking a catalyst for war. Jacob "Jack" Shadow gets caught up in this conflict after losing his family to a terrorist bombing by the Moon's rebel army. Vowing revenge, Jack joins the Earth army as a scout on the Moon, only to discover an unexpected leader among the resistance forces.