Okubo is a minor supporting character in Yu Yu Hakusho, best known as one of Kazuma Kuwabara's closest friends and a member of his small gang. He is a teenager of about fourteen with black hair styled in the same greaser fashion Kuwabara favors, and his tough street-kid appearance matches the delinquent environment the group comes from. Alongside Kirishima and Sawamura, Okubo functions as one of Kuwabara's loyal followers, and by extension he becomes a friendly ally to Yusuke Urameshi and the others connected to Kuwabara's circle.

Okubo's background gives him more depth than a typical background character. His mother is frequently ill and unable to earn enough money for the household, so Okubo takes on a part-time job to help support his family. This responsibility reveals a dependable and hardworking side beneath his rough exterior. Where some delinquent characters are defined purely by fighting or troublemaking, Okubo's motivation is grounded in loyalty and necessity: he wants to help his family survive and he stands by his friends without hesitation. He is described as a trusting person, which fits his willingness to follow Kuwabara and become involved in situations that are far beyond ordinary teenage concerns.

In the story, Okubo appears mostly in the background of Kuwabara's daily life, providing comic relief and reinforcing Kuwabara's role as the leader of a small crew of fellow students. His most significant moment comes during the Chapter Black saga, when he joins Kuwabara, Kirishima, and Sawamura at a Megallica concert. On the way home, the group is attacked by Kiyoshi Mitarai, also known as Seaman, a psychic who uses water-based monsters. Okubo and the others nearly drown in one of these creatures and are saved only when Kuwabara intervenes. Kuwabara then carries all three of them, along with the defeated Mitarai, to Yusuke's apartment before collapsing from exhaustion. After Okubo and his friends explain what happened, Kurama erases their memories of the incident so they are not burdened by the trauma, and they are sent home to resume their ordinary lives. This episode gives Okubo a brief but meaningful role, showing how close he and his friends come to danger simply by being connected to Kuwabara, and it also explains why he remains a normal person rather than becoming more involved in the supernatural side of the series.

Okubo's key relationships center on Kuwabara, whom he treats as a leader and friend, and on his fellow gang members Kirishima and Sawamura, with whom he is almost always seen. He has no notable abilities or combat skills; he is an ordinary human whose strengths are his loyalty, his willingness to work for his family, and his trust in the people around him. His development is limited, as he serves a supporting function rather than undergoing a personal arc. He starts as a minor comic presence and briefly becomes a victim of a supernatural threat, but because of the memory erasure, he ends the story the same person he was at the beginning, with his friendship with Kuwabara intact and his family still his primary concern.