Touma Minami

The only daughter in the other Minami family. She is a tomboy girl in class 5-1 who, despite having the same surname, is not related to the Minami sisters. However, Chiaki adopted her as a little brother because of the same surname. She has three older brothers that know nothing about her. Her tomboy action can be said to be an influence by her brothers. The way she acts, looks and dresses causes Fujioka to actually believe that she is a boy. "Touma" contains the kanji for "winter"; Chiaki declares that Touma is the younger because "winter follows autumn."

(Source: Wikipedia)