Eijirou Kashiwaba is a character who serves as the temporary acting coach for the Meisei High School baseball team. He is a former student of Meisei, and his sudden arrival at the team is initially met with confusion and hostility. The coach, Nishio, had intended to hire Eijirou's older brother, Eiichiro Kashiwaba, but due to a misunderstanding, Eijirou took the position. Eiichiro was a celebrated former captain and ace pitcher for Meisei, remembered as one of the team’s greatest players. Eijirou, by contrast, arrives with a rough, intimidating appearance, often wearing sunglasses, and immediately establishes a strict and harsh atmosphere.

The motivation behind Eijirou’s coaching methods is rooted in a deep and painful personal history. When he was a student, Eijirou was also a talented baseball player who joined the Meisei team. However, he was unjustly expelled from the club. The official reason given was his past as a troubled youth, but the real cause stemmed from lingering resentments within the team from his brother's era. In a pivotal past incident, Eiichiro was involved in a car accident that could have led to the team's disqualification. Eijirou took the blame for his brother to protect Eiichiro’s future and the team's standing. Despite this sacrifice, Eijirou was later cast out, a betrayal that planted deep seeds of bitterness and a desire for revenge against the Meisei baseball program. Consequently, he accepts the coaching position not out of a sense of duty, but with the hidden intention of彻底 destroying the team from within.

Eijirou's personality is best described as a classic example of an exterior that is cold, bitter, and antagonistic, masking a more complex and ultimately passionate interior. At the outset, he is冷酷, speaking in a sharp, sarcastic tone and showing no patience for what he perceives as weakness. He immediately fires Minami Asakura as the team manager, telling her to focus solely on her rhythmic gymnastics, and subjects the players, particularly the ace Tatsuya Uesugi, to grueling, seemingly sadistic training regimens. He makes cruel remarks designed to provoke, such as callously referencing the death of Tatsuya’s twin brother, Kazuya. Despite this villainous facade, evidence suggests that his love for baseball never truly died. His harsh training, while intended to break the players, inadvertently strengthens them. His actions reveal a hidden sense of care, such as when he instinctively shouts to prevent a player from stepping on broken glass. This contradiction, where his harsh actions produce positive results and his faint glimmers of concern slip through, defines his character.

His role in the story is as a catalyzing antagonist. He is the obstacle that forces the Meisei team, and especially Tatsuya, to grow. Eijirou seems to recognize a kindred spirit in Tatsuya, as both are younger brothers living in the shadow of a more talented, admired sibling. He sees his own past in Tatsuya's struggle to step out from Kazuya's memory and pitch for himself. This recognition creates a complex dynamic; he torments Tatsuya the most, but also seems to be the one who understands Tatsuya’s internal conflict. As the story progresses, this relationship shifts from simple antagonism to a grudging, unspoken mutual respect. The final turning point occurs during the crucial regional qualifying game for Koshien, where Eijirou's worsening eye condition leads to temporary blindness. Unable to see, he must rely on Tatsuya's descriptions of the game to formulate his strategies. In this moment of vulnerability, his desire for revenge is completely replaced by his pure, unadulterated desire to win and lead the team to Koshien. His tactical genius from the bench guides Meisei to a dramatic victory, after which he quietly leaves for the hospital to undergo surgery.

Eijirou's development is a powerful arc from bitterness to redemption. He arrives as a man consumed by the past, but through his intense engagement with a team that refuses to give up, he revisits his own love for the game. The successful surgery allows him to recover his sight, and he makes his way to Koshien to watch his team play, having fully shed his vengeful identity and reclaimed his identity as a baseball man. His notable abilities lie not in athletic prowess on the field, but in his sharp, analytical mind. He is a brilliant strategist with an exceptional understanding of baseball tactics, player psychology, and game management. His ability to read a situation and make decisive calls, even when blind, demonstrates that his greatest strength is his baseball intelligence. He possesses a physical toughness and a willpower that allow him to endure the grueling physical demands he places on himself and others, a testament to his own past athleticism and unyielding nature.