Masamune Date, called Date-sensei in the modern era, works as a schoolteacher and descends from the historical feudal lord Date Masamune. Mysterious text messages and the discovery of an ancient scroll in her home trigger her transportation to an alternate dimension mirroring Japan's Warring States period, accidentally bringing her student Yoshino Hide (nicknamed Hideyoshi) along. Within this female-dominated past, she assumes her ancestor's name and position as a daimyo. In the modern world, she appears as a confident, professional educator with fair skin, light blue hair tied in a bun, and yellowish-brown eyes. She wears a white shirt, blue jacket, and pencil skirt. In the Sengoku era, her look transforms: her hair flows freely, and she dons a blue, gold, and white ensemble featuring a bra, long jacket, skirt, boots, gloves, and a crescent moon-emblazoned helmet. An eye patch covers her right eye (alternatively referenced as the left eye in some sources). Her actions in the alternate world stem from a hidden agenda. Learning of the Crimson Armor's legend from a descendant who visited her briefly in the past, she aims to retrieve it to reshape Japan's history under her family's control. She keeps her identity secret, operating solo while sometimes assisting the protagonists. She rescues Hideyoshi multiple times and offers strategic counsel, like advising storytelling to escape a forest. Her involvement climaxes during the recreated Honnouji Incident. She manipulates Akechi Mitsuhide into burning the Honnouji Residence and attempts to steal the Crimson Armor from Oda Nobunaga. Tokugawa Ieyasu thwarts her plan, seizing the armor and falling under its evil influence. After Ieyasu's defeat and the armor's removal, Masamune tries to reclaim it but is stopped by Nobunaga, who destroys the artifact. Her personality shifts with context. As a modern teacher, she is supportive and encouraging, stressing diligence in studies. In the Warring States setting, she adopts an aloof, mysterious air, though her underlying concern for Hideyoshi endures. She possesses no supernatural abilities or combat weapons, relying solely on intellect and subtle influence. Her story concludes when she reveals her true identity to Hideyoshi. Together, they return to the modern world after bidding farewell to Nobunaga and Mitsuhide.