"Aru Kararu no Isan" (also known as "A Certain Magical Index: The Movie – The Miracle of Endymion") is a 2013 anime film set within the "A Certain Magical Index" universe. The story takes place in Academy City, a technologically advanced metropolis where students develop supernatural abilities. The narrative centers around Touma Kamijou, a high school student with the unique ability to negate any supernatural power with his right hand, known as the Imagine Breaker.

The plot begins with the construction of Endymion, a massive space elevator designed to revolutionize space travel and energy distribution. During a routine visit to the construction site, Touma encounters Arisa, a young singer with a mysterious past. Arisa possesses a rare and powerful ability tied to her voice, which attracts the attention of various factions within Academy City. As Touma becomes involved in protecting Arisa, he uncovers a conspiracy involving the space elevator and its true purpose.

The conflict escalates when a powerful organization seeks to exploit Arisa's abilities to control Endymion, which is revealed to be a weapon capable of altering the balance of power between science and magic. Touma, alongside his allies Index, a magical nun with vast knowledge of spells, and Misaka Mikoto, a powerful electromaster, must confront the organization and prevent the misuse of Endymion. The story explores themes of ambition, sacrifice, and the ethical implications of technological advancement, as the characters navigate a world where science and magic collide.

The film maintains the established tone of the series, blending action, supernatural elements, and moral dilemmas. Key characters include Touma Kamijou, whose determination and sense of justice drive the narrative; Arisa, whose abilities and vulnerability make her a central figure in the conflict; and Index and Misaka, who provide support and additional layers to the story. The film expands on the lore of the "A Certain Magical Index" universe while delivering a self-contained narrative that appeals to both longtime fans and newcomers.