Angel Fall Arc

The Angel Fall Arc is a story arc that occurs in the Toaru Majutsu no Index storyline. It concerns with the activation of a world-wide spell known as Angel Fall, a spell that switches the elements, as well as the appearances of persons around the world. The most notable affect of Angel Fall is the expulsion of an angel to earth. The arc focuses on Touma, Kaori and Motoharu trying to find the culprit and stop Angel Fall, while Touma deals with his family that he meets for the first time since losing his memories, during an involuntary vacation outside of Academy City.

Aftermath of the Sisters Arc

 * Main article: Sisters Arc

After defeating Accelerator, delinquents looking for prestige and glory increased their hostilities on Touma as he was the one to have defeated Academy City's strongest esper. Because of this, Touma is forced to leave Academy City (along with Index)at the urging of Tsukuyomi Komoe, while Academy City quell the situation during his absence.

Activation of Angel Fall
Kamijou Touya – Touma's father and collector of souvenirs from all around the world – unitentionally activates Angel Fall after arranging the various souvenirs in his home in accordance to the principles of feng-shui in an effort to stop his son's vast misfortune, and after accidentally leaving his house unlocked to go to Touma's current location.

1st Day
Prior to the start of the arc, Touma makes and agreement with his family in the Oowarai Beach resort. However, for some reason, Touma's family were unable to go to the resort on the appointed day promising that they would arrive the day after, disappointing Index who was eagerly awaiting their arrival.

Throughout the day before meeting his family, Touma becomes considerably anxious and worried of their impending arrival, citing his memory loss as the reason, as he has no idea what his family looks like and what kind of persons they are.

2nd Day
Touma wakes up the next morning, unaware of the change that the world has gone through. Touma meets his father, and though depressed that he could not recognized his face, Touma is content that he finally gets to meet his father.

However, soon discovers something is incredibly wrong, after seeing that nearly everyone he knows from both magic and science side has converged into the resort apparently to pull a prank on him. With Index being his mother, Misaka Mikoto being his cousin Tatsugami Otohime, and Aogami Pierce as Index.

Afternoon
After much trouble, Touma finally realizes that people switching their appearances is too much in a large scale for it to be a mere prank. While pondering about this, Touma is nearly attacked by Misha Kruezhev who suspected Touma to be a spellcaster, however, he saved just in time by Kanzaki Kaori (who he meets for the first time and successfully manage to fool her that he didn't lose his memories) and to his surprise Tsuchimikado Motoharu.

Here, they explain to him that for reasons unknown a magician has cast a spell called Angel Fall, that caused a distortion in the world by forcing an angel class into that of a human class, ruining the balance between the classes and thus switching the content and appearances of humans. Motoharu explains that Touma is the most likely suspect for Angel Fall, as his appearance did not change and is the reason why Misha attacked him. Though, they explain to Misha that Touma could not have been the spellcaster as he is a low-level esper, and that he shows no signs of injuries with use of magic due to him being an esper. Tsuchimikado also states that Touma could not have been the spellcaster as he holds Imagine Breaker, an ability that negates all supernatural phenomenon.

Touma proves his innocence to Misha by cancelling her magical directed attack on him as a test. However, the spell is still centered around Touma, which indicates that someone close to Touma might've been the one to have cast Angel Fall. Touma later demands how Motoharu knows of his Imagine Breaker and his knowledge regarding the magic side, to which Motoharu replies that he is also a member of Necessarius.

Trivia

 * This arc is notable for being highly edited for the anime adaptation, notably the removal of Hino Jinsaku.
 * This arc does not appear in the manga version, though some of the characters that appear in the arc, is featured in a short omake. Also, it is shown that Touma and Index some how went to the beach, though this it is not shown whether or not the events of this arc actually occurred off-screen.