Akio Kazama, husband to Mrs. Kazama and adoptive father of Shun Kazama, works on a boat by day and relaxes by watching baseball on television in the evenings. His family lives in Yokohama. Following the loss of their newborn child, Akio and his wife adopted infant Shun. This began when their close friend, Yūichirō Sawamura, brought Shun to them shortly after World War II. Sawamura explained that Shun's biological parents had perished—his father, Hiroshi Tachibana, in a repatriation ship accident, and his mother during childbirth—with no other relatives surviving due to the Nagasaki bombing. Sawamura had initially registered Shun under his own name to prevent orphanhood but sought a permanent family for him. Akio and his wife willingly took Shun in, raising him as their own son.

Though Shun sometimes inquired about his biological parents, Akio consistently reaffirmed that Shun was his son in every meaningful sense, emphasizing their bond over blood relation. Despite their closeness, Shun did not share his romantic feelings for Umi Matsuzaki with Akio. Akio learned of their relationship only when Umi's mother, Ryōko Matsuzawa, telephoned him. Recognizing Shun's distress over the potential familial tie to Umi—initially feared to be his half-sister—Akio directed Shun to seek answers from Yoshio Onodera, a ship captain and mutual acquaintance of their fathers. This guidance proved pivotal in resolving Shun and Umi's misunderstanding about their lineage.

Akio provided steadfast support and care throughout Shun's upbringing. His longstanding friendship with Yūichirō Sawamura saw Sawamura frequently visit to offer financial and emotional support during Shun's early years. Akio's actions during the film's events, particularly his crucial direction toward Onodera, clarified Shun's true parentage and enabled his relationship with Umi. Akio's character is defined by his dedication to family, his labor-intensive profession, and his understated yet essential role in achieving the narrative's resolution.