Kōichi Tabuchi appears as a star baseball player for the Seibu Lions, caricaturing the real professional player renowned for his powerful hitting as a catcher, first baseman, and cleanup hitter. His character builds directly on the real Tabuchi's career, including his time with the Hanshin Tigers before joining the Seibu Lions. Official media reflects documented events from the real player's life, such as a significant 1970 beaning incident requiring hospitalization that spurred the adoption of ear-flapped helmets in Japanese baseball, though the manga starts during his later struggles with performance and weight gain.

Within manga and anime adaptations, the character encounters persistent challenges tied to his physical condition and athletic performance. In "Gekitō Pennant Race," his difficulties manifest symbolically through a fading shadow, signifying declining physical and mental health. This deterioration impacts his gameplay, contributing to team losses and leading teammates to organize "Tabuchi Day" to improve his morale, an effort initially unsuccessful. His emotional journey includes depression, which lifts when a character named Miyoko, depicted as his wife in the manga, dresses as a cheerleader to support him.

His interactions involve caricatured portrayals of real-life baseball figures like teammates Yasuda and Kakefu, and rival Sadaharu Oh. Despite often critical or humorous depictions—including scenes of fan disapproval or ostracization—the real Kōichi Tabuchi endorsed the character, crediting the manga for facilitating his meeting with his actual wife and expressing appreciation for the series. The character's narrative remains consistent across subsequent manga volumes and the three anime films.