A Certain Magical Index Episode 21 English Dubbed Episode Title:Identity Unknown (Counter Stop).Episode Description:Tōma returns to school after summer break but is followed by Index, who thinks she will not have anything to eat for lunch while he is away at school. Arriving at school, he learns that Komoe is doing research on AIM (An Involuntary Movement), a diffusion field of power that espers emit. When Index arrives in class, Komoe sends her away and then introduces Aisa as the new transfer student. Instead of leaving, Index runs into another transfer student, Hyōka Kazakiri, and befriends her. When Tōma finds them later, Komoe catches Tōma skipping the opening ceremony and Hyōka mysteriously vanishes. Aisa becomes suspicious of Hyōka, recalling her as the top student at her old school who was never seen, and warns Tōma and Komoe about her. Meanwhile, Tsuchimikado meets with Aleister concerning the illegal arrival of a Necessarius mage named Sherry Cromwell in Academy City and, despite Tsuchimikado's offer to take care of Sherry discreetly to preserve the peace between Necessarius and Academy City, Aleister wants Tōma to defeat her, as his involvement will help the "key" to the Five-Element Agency. As Tōma, Index and Hyōka head to an underground mall for lunch, Kuroko finds Sherry and attacks her unsuccessfully when the latter summons a golem. Though Kuroko is saved by Mikoto, Sherry escapes and casts a spell to send eyeballs throughout the city.