Kōnosuke Nakane is the youngest child born to Otokichi and Yoshi Nakane during the narrative. His older siblings are Kayoko, Tadayoshi, Takejirou, and Kisaburou. His mother was visibly carrying him at the story's start, and his birth happens midway through the timeline, marking a significant family event as wartime hardships increase.

As an infant, Kōnosuke learns to crawl. On one occasion, he wanders off while Kayoko watches him, drawn by nearby cats he tries to imitate. His distress mirrors Kayoko's when he cries upon seeing her cry after this brief separation, showing early emotional connection.

Kōnosuke represents familial hope and continuity amidst Japan's escalating conflict, though the war's broader consequences affect him indirectly. Promotional materials for the work often featured him prominently as an "Advertised Extra," despite his late introduction and limited direct involvement in key events.

During the 1945 firebombing of Tokyo, Kōnosuke is in the city with his parents and grandmother. He dies alongside them in the destruction. Later, Kayoko searches the devastated city and hears a boy's name called. She initially mistakes it for Kōnosuke—a fleeting moment emphasizing his absence when the child is revealed to be another boy.