Gisen Yagyu (?? ??, Yagy? Gisen)
Voiced by: Kaoru Mizuhara (Japanese); Melissa Davis (Season 1), Jessica Boone (Season 2) (English)
The series' main antagonist. Gisen is a young girl sporting an eyepatch over her right eye who falls naked from the sky into Muneakira's arms, much like Jubei did. She is initially friendly and demure, but is shown to be very perverse when around Muneakira (whom she refers to as "Master"). She is continually trying to "tuck" a certain part of his body between her breasts; the reason being is that she thinks that the relationship between a general and a samurai is similar to that of a master and slave. Jubei nickname for Gisen is "Gittan", and Gisen refers to Jubei as "onee-sama" (big sister).
It is later revealed that she is a Master Samurai, with the contractual mark on her right eye. Her general is Amakusa Shir?, a powerful samurai who once aspired to destroy Japan until he was killed by a group of rebels. She intends to revive him to destroy Japan once more. Her true personality is also revealed throughout the story, revealing her as a highly sadistic person who will stop at nothing to ensure her general's revival; she even attempted to take Jubei's body into her own to further the process. Her transformation phrase is "Inka Ry?ran", which means "Indecent Flower Blooming Profusely", and her attacks usually involve ice. Gisen's right eye (colored red) can control and manipulate people's minds, and she wields a blade that can turn into a scissor-like weapon.