Natsumaru served as an onna-bugeisha among Oda Nobunaga's seven samurai, wielding her sword and wearing a pendant bearing her family crest—an heirloom passed from mother to daughter. She first encountered Yasuke when thanking him for saving her younger brother at a trade port; this forged a connection between two warriors facing discrimination within Nobunaga’s ranks, hers due to gender and his due to foreign origins. Secretly, she operated as a besshikime—a personal guard and spy for Iga clan leader Hattori Hanzo. This dual role demanded she gather intelligence on Nobunaga’s forces while maintaining her position as a trusted retainer. Though genuine affection for Yasuke grew, her paramount loyalty remained with the Iga clan, compelling her covert actions. Her espionage unraveled during the Tenshō Iga War. Yasuke discovered her allegiance after recognizing her family crest on fallen Iga fighters. When Nobunaga’s forces ambushed Hanzo’s army using her leaked intelligence, Yasuke confronted her on the battlefield. She confessed her loyalty to Hanzo and attacked Yasuke, forcing him to kill her in combat. With final words, she absolved him of guilt and acknowledged his honor. Her death haunted Yasuke for decades, embodying his unresolved grief and moral conflict. Years later, he visited her grave and returned her sword to her brother, withholding the truth of her betrayal. This act secured his closure while preserving her legacy as a warrior in her family’s memory.