Kisaburō Nakane is the third son and middle child of the Nakane family, with older brothers Tadayoshi and Takejiro and a younger sister named Kayoko. His background is defined by the close, though sometimes complicated, bond he shares with his sister. While he occasionally joins his older brothers in teasing Kayoko, he is generally not the primary instigator of such behavior. His protective instincts are much stronger, as demonstrated when he decisively intervenes to defend Kayoko from neighborhood bullies, brandishing a stick and driving them away after they ruin her dress.

The most significant event in Kisaburō’s life is surviving the Tokyo firebombings, a traumatic turning point that sees the rest of his immediate family perish. He escapes by climbing through an open window to find shelter, emerging physically unharmed but emotionally shattered. Following this devastation, he travels alone to Numazu, where Kayoko had been evacuated to their aunt’s home. Upon his arrival, he is visibly distressed and delivers the devastating news of their family’s death, an act that underscores his profound psychological trauma and his resilience in the face of overwhelming loss.

His motivations shift dramatically after this tragedy. Initially driven by a need to protect his sister from smaller harms, he becomes solely focused on survival and maintaining their bond as their only remaining family. Following their reunion, Kisaburō and Kayoko return together to the ruins of Tokyo, relying exclusively on each other for both emotional and practical support. This shared grief forges them into a dedicated brother-sister team, navigating the challenges of the destroyed city and an uncertain future together. Their relationship evolves from a typical sibling dynamic into a deep, mutually supportive partnership, as seen when Kayoko intervenes with their parents after he runs away following a fight, reinforcing their mutual reliance.

Kisaburō’s role in the story is central to its exploration of loss and resilience. His key relationships are almost entirely defined by his connection to Kayoko, with whom he shares a status of often being in accident-prone or embarrassing situations. A notable ability is his readiness for physical defense when protecting his sister, though his most significant strength lies in his psychological endurance, surviving the firebombings and the emotional aftermath to continue forward. The final scenes of his narrative depict him conversing with Kayoko amidst the devastation, confirming their continued partnership as they face an uncertain future together.