Tetsuo Kasamatsu serves as the patriarch of the Kasamatsu family in Midori Ward, Nagoya, Japan during World War II. He shares his home with wife Tomoko Kasamatsu and young son Yusuke Kasamatsu. Responding to wartime government directives, Tetsuo constructs a sturdy, spacious air raid shelter beneath their house with Yusuke's assistance. Shortly after completing the shelter, Tetsuo is conscripted into the Kwantung Army and deployed to China, compelling seven-or-eight-year-old Yusuke to assume the role of household's primary male figure.

Following Tetsuo's deployment, American B-29 bombers target Nagoya in repeated air raids after Saipan's fall in late 1944, striking industrial zones like the Mitsubishi Aircraft Works and inflicting both physical destruction and psychological trauma. During these bombings and evacuations, Yusuke retreats to the shelter where he experiences recurring hallucinations of Tetsuo's presence. In these visions, Tetsuo provides emotional comfort and reinforces Yusuke's responsibilities as man of the house. Yusuke fixates on this imagined paternal presence, refusing to acknowledge Tetsuo's potential death in combat. This hallucinatory companionship becomes Yusuke's core coping mechanism throughout the traumatic events.

Tetsuo's impact transcends the war. Sixty years later, elderly Yusuke visits the park now occupying his former homestead and shelter site, demonstrating the enduring trauma of his father's absence and wartime experiences. Tetsuo Kasamatsu's narrative significance stems from his physical absence post-deployment, his creation of the shelter, and his lasting psychological influence on Yusuke. His presence manifests exclusively through Yusuke's wartime hallucinations and memories.