Eyes: Dark brown, with eye-patch over left eye
Height: 157 cm
Weight: 45 kg
Kyubei is an aristocratic young lady who was brought up as a male in order to succeed her family's clan. She dresses and behaves like a boy due to her upbringing, but occasionally shows her more feminine side, and appears to be interested in clothing in the gothic lolita style.
She was close friends with Otae when they were children (and is in fact in love with her), and lost her left eye protecting her when they were young. As a result of this incident, Kyubei now wears an eye-patch across her left eye. The incident also left her with the determination to make herself stronger, and for many years she was training hard to improve her skills.
When she returned shortly before her appearance in chapter 110, she has already mastered the Yagyu-Ryu sword technique. Her strength is just below her grandfather's.
Her name is based on the historical Yagyu Jubei, who also had an eye patch.