Ep. 1: Naoyuki saves Iriya at the pool and discovers her mysterious wrist caps before she transfers to his school.

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On the final day of summer vacation, Naoyuki visits his school pool after a forty-day trip with Kunihiro investigating the Sonohara base. There, he encounters Iriya, who falls into the shallow water while he assumes she is drowning. After rescuing her and treating a nosebleed, he teaches her to swim and notices silver circular caps on her wrists that she claims taste like electricity. A military siren interrupts them, and Enomoto orders Naoyuki to leave. As he passes through a military blockade, he receives a bug implanted in the upper-right part of his neck. The following day, Iriya arrives at school as a transfer student. During the opening ceremony, an air raid drill alarm sounds, causing Iriya to drag Naoyuki into a secured shelter, believing a real attack is imminent. Inside, after losing a game, Iriya collapses. While Naoyuki attempts to treat her, Shiina and others open the shelter, catching him in an awkward position.