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 in his 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.
夏休み最後の夜、浅羽直之は学校のプールに忍び込んだ。誰もいないプールで存分に泳ぐつもりだったのだ。しかし、そこには水着の少女がいた。名前は伊里野加奈。彼女の手首には、なぜか金属の球体が埋め込まれていた。浅羽が伊里野に泳ぎ方を教えていると、不意にサイレンが鳴り、"伊里野の兄貴みたいなもの"と名乗る男が現れる。有無を言わさずプールから立ち去るように言われた浅羽の耳に、奇妙な言葉が飛び込んでくる。「戦争は1947年から始まってた、みんな気付いてなかっただけ」
