Ryuuka Jihiyou  

, 慈悲王リュウカ

The character you're referring to is the protagonist of "The Hanaukyo Family," a manga series by Takeshi Obata and Clamp Studio. She is a young woman who aspires to become the head of her rival family, the Hanaukys, after her father passes away. However, she becomes frustrated when she learns that if she marries the current head of the Hanaukyo family, she will inherit his position. The character finds herself drawn to this man despite his small stature and whiny personality. She is a fan of military themes and later competes with another character named Mariel in a series of challenges to prove her worth as a member of the household. Despite her bluntness and short temper, she eventually becomes more fond of Ryuukas home and its handsome male staff members.