Saitō Kichō originates from 1549 during Japan's Warring States period, betrothed to Oda Nobunaga in a political marriage arranged by her father, Saitō Dōsan. She arrives inexplicably in the modern era within the storeroom of Nobunaga Oda's family home. Aged 15 by traditional Japanese reckoning, she initially maintains a cool, detached demeanor and an uninterested gaze.

Her background is marked by political turmoil. Before her engagement to Nobunaga, she was briefly married to Toki Yorozumi as part of another alliance. This marriage ended with Yorozumi's death after he attacked Mino, leaving Kichō a widow at 13. This experience cemented her conviction that her primary duty is protecting her domain through strategic marriages and producing heirs. Mistaking the modern Nobunaga Oda—a middle school teacher descended from or potentially reincarnated from the historical figure—for her intended husband, she persistently urges him to conceive a child with her, viewing this as essential to her role.

Kichō's development focuses on adapting to modern life and reassessing her purpose. Enrolled in middle school by Nobunaga, she struggles with the unfamiliar environment but gradually adjusts. Later residing at Gifu Castle, she gains insights into Mino's historical fate and the Warring States period's outcomes. Exposure to modern life and these historical revelations gradually shift her priorities; her singular focus on bearing an heir evolves into a desire to remain permanently in the present and become Nobunaga Oda's lawful wife, moving beyond viewing herself solely as a political instrument. Nevertheless, she continues referencing the importance of producing an heir, reflecting enduring ties to her historical obligations.

Her arc concludes with an explicit decision to stay in the modern era, solidifying her emotional attachment to Nobunaga and acceptance of her new life.