Miku is a minor supporting character in Catch Me at the Ballpark!. A four-year-old girl, she visits the Chiba MotorSuns Stadium with her family during a baseball game and becomes separated from them. Lost and distressed in the crowd, Miku approaches the beer vendor Ruriko for help. Ruriko brings her to the veteran security guard Ryuichi Igarashi, who then instructs his younger partner Reiji Takimoto to calm Miku with candy. After Miku is safely reunited with her parents, the incident inspires Takimoto to take his job more seriously, marking a turning point in his own character development.

Miku’s role in the story is brief but thematically significant. Her presence highlights the ballpark as a community space where staff and strangers look out for one another. She has no further appearances or development beyond this single episode, and no special abilities are shown. Her personality is not elaborated beyond the typical behavior of a scared, lost child who seeks adult assistance. Her key relationships are with her parents, who are briefly seen picking her up, and indirectly with Ruriko and the security guards who facilitate her safe return. Miku serves as a catalyst for another character’s growth rather than undergoing any arc of her own.