Jubei-chan: The Ninja Girl is a Japanese anime action comedy television series created by Akitaro Daichi (Fruits Basket, Tsukikage Ran). Jubei-chan follows Jiyu Nanohana, a modern highschool girl and unwilling heir to the Yagyu Jubei school of swordsmanship. The series is recognized for its magical girl stylings, including a mystical artifact, the Lovely Eyepatch, that serves as the source of the heroine's power.
Jubei-chan comprises two television series. The Secret of the Lovely Eyepatch premiered April 5, 1999 and revolves around Jiyu Nanohana coping with her newly entrusted powers and responsibilities and the centuries-old feud between the Yagyu and Ryujoji schools.
The main conflict in The Secret of the Lovely Eyepatch is between the Yagyu Jubei and Ryujoji schools. The rivalry was seemingly ended 300 years before the events of the series, when Yagyu Jubei defeated the Ryujoji school champion. Dying from his wounds, Jubei told his loyal companion Koinosuke to find someone with "plump, bouncy bon bons" and give her his eyepatch that contained a lifetime's worth of sword techniques. Unknowingly to Koinosuke, the Ryujoji clan plots their revenge.
After 300 years of searching, Koinosuke finds Jiyu Nanohana in modern Japan. Her figure makes her the ideal candidate to be the next Jubei. He approaches her and tries to give her the eyepatch but she steadfastly refuses. Only when they are attacked by a Ryujoji swordsman does she don the eyepatch and dispose of him. They eventually find out that the Ryujoji clan believes it will be vindicated once the reincarnation of Jubei is defeated.
The introductory episodes follow the "Monster of the Week" formula, in this case, her teachers and peers constantly challenging her. Later episodes delve into Sai's pain of losing Jiyu's mother, the sacrifice that Jiyu has to make in order to live a double-life as Jubei, and the Ryujoji Family Curse.