"Iriya no Sora, UFO no Natsu" is a science fiction and romance manga series that intertwines themes of adolescence, extraterrestrial phenomena, and military intrigue. The story is set in a near-future Japan, where the protagonist, Naoyuki Iriya, is a high school student and aspiring journalist. Naoyuki becomes involved with a mysterious girl named Iriya Kana, who is revealed to be a test pilot for a secret military project involving advanced aircraft technology. The narrative explores their growing relationship as Naoyuki uncovers the truth about Iriya's connection to a classified program aimed at defending Earth from an impending alien threat.

The plot deepens as Naoyuki learns that Iriya is not only a skilled pilot but also a key figure in the military's efforts to combat extraterrestrial forces. Her aircraft, the "UFO," is a highly advanced machine designed to intercept and neutralize alien incursions. As Naoyuki becomes more entangled in Iriya's world, he discovers the emotional and physical toll the program takes on her, as well as the ethical dilemmas surrounding the use of child soldiers in such high-stakes operations. The story balances moments of tender romance with intense action sequences, as the characters grapple with their roles in a larger, intergalactic conflict.

The manga also delves into the psychological and emotional struggles of its characters, particularly Iriya, who bears the weight of her responsibilities while yearning for a normal life. Naoyuki's perspective as an outsider provides a lens through which the reader can explore the moral complexities of the military's actions and the sacrifices demanded of those involved. The narrative builds toward a climactic confrontation with the alien forces, raising questions about humanity's place in the universe and the cost of survival.

The main characters are Naoyuki Iriya, whose curiosity and determination drive much of the story, and Iriya Kana, whose strength and vulnerability make her a compelling figure. Supporting characters include members of the military project, who provide additional context and stakes to the unfolding events. The manga's blend of personal drama, speculative science fiction, and action creates a multifaceted story that appeals to fans of both genres.