Kenta Saitou is an elementary school-aged orphan living in Tokyo during World War II with his sister, Tomoko Saitou. After the death of their parents, the siblings endure wartime hardships, relying on resilience and mutual dependence for survival. Kenta shares a close bond with his sister, who suffers from illness; this relationship defines his daily life, compelling him to shoulder responsibilities for her care amidst the scarcity and chaos of war.

When Ayaka Nakanishi arrives from the future just days before the Tokyo firebombings, Kenta encounters her. He shelters and assists Ayaka as she struggles in the dangerous, unfamiliar environment. Kenta demonstrates practical resourcefulness and a protective instinct, particularly during life-threatening air raids. His background as an orphan shapes his perspective, fostering self-reliance while highlighting his reliance on Tomoko and their makeshift community. The war forces Kenta to confront extreme challenges like resource shortages and constant safety threats, influencing his decisions. His aid to Ayaka illustrates his capacity for empathy and assistance despite his own precarious situation.

Kenta's experiences show his adaptation to adversity. The loss of his parents and the ongoing war necessitate maturity beyond his years as he navigates survival, protects Tomoko, and helps others in need. His journey reflects a child's resilience during conflict, rooted in these relationships and the historical setting.