Fumio Okada is a minor character in Golden Kamuy, serving as a soldier in the Imperial Japanese Army's 7th Division. He is part of a squad that includes fellow soldiers Genjirou Tanigaki, Tamai, and Noma. His background is that of a regular military man, having served with his unit, where he was once stationed in a wooden building with other soldiers like Hyakunosuke Ogata during a blizzard.

In terms of personality, Okada does not display any distinctive individual traits, primarily acting as a supporting member of his military unit. His main role in the story occurs during the Escape King Arc, where he and his squad are tasked with tracking down the protagonists, Saichi Sugimoto and Asirpa. The soldiers find the hut where Sugimoto and Asirpa had stayed and, following a clue left by the injured Ogata, deduce that their assailant is a man known as the "Immortal". Okada is part of the group that chases Sugimoto and Asirpa on skis through the snowy wilderness. When they corner Sugimoto near a bear's den, Okada and his comrade Tamai initially believe they may have the wrong man, but their suspicion is confirmed by Noma, who recognizes Sugimoto from the war.

His notable abilities are not explored in depth, but as a member of the 7th Division, he is a trained soldier equipped with a standard Arisaka Type 30 rifle. Development is not a factor for this character, as his appearance in the narrative is brief and he does not undergo any significant change. His key relationships are solely with his squad mates. His story ends abruptly and fatally during the confrontation with Sugimoto. When a massive brown bear is startled from its den by the soldiers' gunfire, it attacks the group. In the ensuing chaos, the wounded Tamai fires his weapon erratically, and a bullet accidentally strikes Okada, killing him instantly. His death is a direct result of the unpredictable and dangerous chain of events set off by Sugimoto's actions.