Sadaharu Nikaidō serves as the ace pitcher leading Midoriyama High School's baseball team in the OVA series "Midoriyama Kōkō Kōshien-hen." He stands as a central figure driving the team’s journey to the Koshien tournament, where they overcome formidable opponents. The series, directed by Masashi Ikeda and animated by Light Foot and Studio DEEN, features a distinct visual style. No official media—including seasons, movies, OVAs, or spin-offs—explores his background story, personality traits, relationships, or character development. Other characters named Nikaidō exist in unrelated franchises like "Dorohedoro" and "Saint Liliana Academy," but these are entirely distinct individuals.