Naoyuki Asaba, the quiet and reserved main protagonist and narrator, attends Class 2-4 at Sonohara Junior High. His parents run a hair salon, giving him practical hair-cutting skills he occasionally uses on fellow students within the school newspaper club's facilities. He is a member of this club, the Sonohara Radio News Club, participating in summer UFO-watching activities near a local military base. His sensitive nature makes him emotionally vulnerable, prone to crying during distress, and he is easily influenced by others, particularly the club's energetic president, Kunihiro Suizenji, whose unconventional projects often involve him.

His life shifts dramatically on the final day of summer break during a late-night swim at the school pool. There, he encounters the mysterious transfer student, Kana Iriya, discovers she cannot swim, and offers to teach her. This encounter ignites a deep emotional attachment to Iriya. Unaware of classmate Akiho Sudou's romantic feelings, his growing relationship with Iriya creates tension.

Throughout the story, he becomes intensely protective of Iriya as he uncovers her burdens: piloting the advanced fighter jet "Black Manta," her deteriorating physical condition from piloting stress manifesting in nosebleeds and seizures, and her role in a secret war against alien forces. Witnessing her social isolation and health struggles firsthand drives his determination to support her. This culminates in actions like helping her elope from the military base, where he cuts her hair short, symbolizing a break from her past.

Naoyuki evolves from passivity to assertiveness, defying military figures like Enomoto and Shiina to shield Iriya. His emotional resilience is tested during her physical collapses and the story's climactic events, confronting the reality of her fate within humanity's conflict.