Fifteen-year-old samurai warrior Fubukimaru is the heir to the Kasuga family after her parents, lord and lady of Kasuga Castle, were slain by Unkokusai's henchman Matabi Nekonoshi. The castle fell and her sister Yukino was captured. With no male heir, Fubukimaru's father raised her as a boy to fulfill the successor role, compelling her to conceal her true gender identity. Driven by a prophecy naming "three heroes and one dog" as the castle's saviors, she journeys seeking aid to rescue Yukino. She identifies the time-traveling Nohara family and their dog Shiro as these saviors, recruiting them after Unkokusai's forces steal the family's important personal belongings. Fubukimaru rigorously maintains her male disguise, often declaring "I... am NOT a woman!" when questioned. Her internal conflict surfaces through dialogue revealing the pressure to embody masculine warrior ideals, such as stating it was "not when forced to man" herself in critical moments. Her true gender is discovered by Shinnosuke and Shiro during a hot spring bath, prompting her to reveal the reason for her deception. She demonstrates formidable swordsmanship in combat, defeating numerous soldiers and Unkokusai's henchmen while wielding both a sword and a dagger, often using two hands. Her horse is a favored companion. Confronting Unkokusai, she paralyzes the henchwoman Ogin with a toxin-coated dagger and is herself incapacitated by the poison. Helpless, she entrusts her sword to Shinnosuke, urging him to defeat Unkokusai. Following Unkokusai's defeat, Yukino is revealed alive but unexpectedly disclosed as biologically male despite presenting as female. Fubukimaru reunites with Yukino and later experiences a dream where her deceased mother appears, smiling and encouraging her to continue her duties. Fubukimaru is a lesbian with romantic feelings toward Ring, the Time Patrol officer from the 30th century. Her character arc remains confined to the events of this film.