Yagyuu, Kyuubei

柳生九兵衛

Kyuubei is the sole heir to the Yagyuu family, the daughter of Yagyuu Koshinori and granddaughter of Yagyuu Binbokusai. Raised as a male, she adheres to the samurai code. A genius swordsman, she surpasses average practitioners in skill and can hold her own against veterans like Hijikata Toushirou and Sakata Gintoki.
Upon her introduction, she attempted to take Shimura Tae as her fiancée, though Shimura Shinpachi and others intervened to stop her. She still harbors feelings for Tae, although their relationship remains friendly. She typically follows Tae wherever she goes and mimics her actions. She also protects Tae from the stalker Kondou Isao.
Toujou Ayumu constantly guards her, to the point of being overprotective. Ayumu also tries to convince her to wear gothic lolita outfits, which irritates her, causing her to blast or beat him up for it.
In recent Gintama chapters, she became the target of Katsura Kotarou's jealousy, as he felt she was recently receiving more spotlight in the manga than him.
Kyuubei has a somewhat cold personality, likely due to her rigorous training to become strong. However, Tae's influence is currently shaping a softer Kyuubei, as they spend more time together during their free hours.
She also has an automatic reflex against men who touch her or whom she touches (though she did rescue Gin one time by catching his hand).
In episode 190, it is revealed that, apparently, she really likes Otae's cooking.
Her name probably refers to the famous samurai Yagyu Jubei Mitsuyoshi, due to "Ju" meaning "Ten" and "Kyu" meaning "Nine."