Sachiko Nishio, daughter of Meisei High baseball coach Shigenori Nishio, serves as the team's manager. She befriends Minami Asakura and encourages her to also become a manager. When her father requires hospitalization during the team's senior year, necessitating an interim coach, Sachiko continues steadfastly supporting the team.

Kind and gentle, Sachiko significantly impacts those around her. A childhood friend of the Uesugi twins, Tatsuya and Kazuya, she harbors long-term unrequited feelings for Kazuya, despite his affection for Minami Asakura. Her loyalty remains constant as she provides support through baseball games and personal challenges.

She overcomes personal obstacles and a rocky relationship with her mother with help from friends and family. Later, she becomes the girlfriend of Meisei's former ace pitcher, Takeshi Kuroki. Together, they recognize Tatsuya Uesugi's baseball potential and actively attempt to recruit him for the team.

In "Touch 2: Sayonara no Okurimono," Sachiko appears alongside other supporting characters during events involving rival player Akio Nitta, who sees potential in Tatsuya. Her dedicated role as Meisei's team manager persists, emphasizing her commitment to the baseball program.