Tập 1: Naoyuki cứu Iriya tại bể bơi và phát hiện ra những chiếc băng cổ tay bí ẩn của cô trước khi cô chuyển đến trường của anh.

1

On the last day of summer vacation, Naoyuki goes to school for intending to swim after his forty-day long trip with Kunihiro investigating the Sonohara base. At the school pool, he meets Iriya who in equal surprise falls into the shallow pool, thinking that she is drowning. Saving her and treating her subsequent nose bleed, he begins to teach her how to swim. He discovers silver circular caps on her wrists that she says taste like electricity. A military siren interrupts them, and Enomoto appears, telling Naoyuki to leave first. Passing through the military blockade, he receives a bug planted in the upper-right part of his neck. The next day, he Iriya appears at school as a transfer student. After the opening ceremony, an air raid drill alarm sounds, causing Iriya to take Naoyuki and run into the secured shelter under the impression that a real air raid was about to occur. Inside, after losing a game, Iriya collapses. While trying to treat her, he is caught in an awkward position when Shiina and some other open the shelter. (Source: Wikipedia)