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 Sunohara 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…