Koichiro Mutoh, a 44-year-old Japanese lights engineer at a stage production company, balances pragmatism with quiet optimism as a devoted husband to Mari and father to Ayumu and Go. Tall and broad-shouldered, his short black hair frames a face often set in determined focus, his wardrobe favoring construction gear or a simple green shirt and jeans.

During a routine stadium assignment, a catastrophic earthquake strikes. Secured by safety ropes, he survives the initial collapse, evacuates his team, and races home on a scooter through a fractured cityscape—dodging debris, skirting a collapsed bridge. Reuniting with his family on a hillside, he improvises bandages for Go’s injured eye before guiding them westward, heeding survival advice over chaotic rumors.

His choices weave practicality with empathy: permitting Ayumu to spare water for stranded elders, hunting a boar to stave off hunger. But when scavenging yams to respect Ayumu’s vegetarianism, his shovel strikes a buried wartime bomb. The detonation claims his life abruptly, severing the family’s fragile stability and etching trauma into their journey.

His name—"航" (navigation), "一" (one), "郎" (son)—hints at leadership, while "Mutoh" (武藤: "military wisteria") echoes resilience and entanglement. Koichiro’s steadfast loyalty and survival instincts anchor his family until his sudden demise, a stark pivot underscoring the narrative’s meditation on transience and grief.