Kagefusa Manyuu

Chifusa's sadistic, older sister. Unlike Chifusa, she is perfectly happy with her family's form of government and goes to great lengths to preserve it. She hates her sister because even though Chifusa has a smaller chest than her, she was still chosen as the Manyū successor over Kagefusa. At the beginning of both the anime and the manga, Chifusa steals Kagefusa's breasts when she unwittingly uses the Breast Flow technique for the first time. After this incident, Kagefusa is forced to wear an inflating bra and she swears a personal vengeance against her sister. She eventually abandons this grudge after Chifusa promsies to return her breasts when she masters the Breast Flow technique.

After forgiving Chifusa, Kagefusa's attitude towards life and the Manyu completely changes, turning her into an easygoing and relaxed (albeit still sadistic) person. (Source: Wikipedia)