Goro Ōyama coaches the Meisei High School baseball team. He moved from Kyushu with his daughter Haruka Ōyama after accepting the coaching position near the end of her junior high school year. They live above a ramen shop close to the school. Goro is a Meisei High alumnus who served as baseball team captain and was teammates with Eisuke Tachibana, forging a lasting friendship.

Professionally, Goro began coaching with a spontaneous "just go for it" attitude, focusing on assessing the team's capabilities without long-term plans. He initially did not expect the team to reach the semi-finals, intending to use the first year purely for evaluation. His daughter Haruka played a pivotal role in helping him recognize the necessity for more careful strategic planning. His growth as a coach is evident in his evolving methods; he learns to leverage Haruka's scouting talents and analytical insights, which often surpass his own understanding of the game.

Personally, he is separated from his wife, author Nagisa Tsukikage, though they remain undivorced. Haruka moved to Tokyo with him.

Regarding team development, Goro initially planned to keep first-year player Toma Tachibana with other newcomers. However, after observing Toma's pitching ability and gaining approval from senior players, he designated Toma as Meisei's ace pitcher. He also quickly acknowledged Souichirou Tachibana's exceptional catching skills but expressed confusion over Souichirou's decision to stop pitching, noting the absence of a reliable catcher when Souichirou pitched compared to the established battery partnership between the brothers.

His coaching style gradually shifts from improvisation to structured leadership, incorporating lessons from past oversights. This includes fostering the development of key players like Toma and Souichirou while balancing input from his daughter and adapting his approach based on the team's evolving needs.