Mama leads the Amatsuka family and serves as CEO of a theatrical agency. She possesses a striking physical presence and a resolute personality; her daughters observe that once she decides something, she disregards all opposition. When Yōtarō Amatsuka, a first-year high school student, is orphaned after his last relative dies, Mama adopts him. She welcomes him into her existing household, which includes her 19 biological daughters ranging in age from several months to 18 years old at the time of his arrival. As the family matriarch, she provides a home for all her children. Within the family dynamic, Mama oversees the household and delegates responsibilities, with the eldest daughter Miharu acting as head in her absence.