Mayumi Tachibana, originally Mayumi Sawai, is the mother of Soichiro and Otomi Tachibana and the step-mother of Touma Tachibana. She married Eisuke Tachibana, a widower, when Touma was six years old, bringing her own two children into the new household. Her personality is loving and talkative, and she is very open about her family situation. Beneath her cheerful and energetic exterior, there are subtle indications of a more complicated history in her life before the story begins. Her primary motivation is to support her blended family, encouraging her children and step-son in their baseball aspirations and maintaining a warm, cohesive home environment. In the story, she serves as a supportive parent figure, often appearing in domestic scenes or communicating with her children by phone. Her key relationships are with her husband Eisuke, her sons Soichiro and Touma, and her daughter Otomi. She does not undergo major foreground character development, but her background as a widow who remarried adds depth to the family dynamics explored in the series. She possesses no notable athletic or combat abilities; her role is defined by her nurturing and communicative nature.