Nozomi Kasuga is a second-year high school student transported to an alternate world resembling Genpei War-era Kyoto alongside her childhood friends, Masaomi and Yuzuru Arikawa. Identified as the Hakuryū no Miko (Priestess of the White Dragon), she is chosen by the dragon god Hakuryū to seal vengeful spirits unleashed by the Heike clan to disrupt the natural energy flow and weaken the Genji. Her primary goal becomes restoring Hakuryū's power to return home, leading her to ally with the Genji forces.

Adapting from an ordinary student to a spiritual leader and combatant, she demonstrates resilience fighting alongside the Eight Guardians. Her development intensifies after witnessing comrades die in a failed battle, triggering the acquisition of time-travel abilities through the White Dragon's scale. This power allows her to revisit past events, alter fates, prevent tragedies, and reflect her determination to protect others beyond initial failures.

Her journey is deeply shaped by relationships. She shares a strong bond with the Arikawa brothers. Masaomi, her childhood friend and romantic interest, is revealed as the Heike general Kaeri Naifu, forcing them onto opposing sides. Yuzuru, Masaomi's younger brother, harbors unrequited feelings for her, adding emotional complexity. Her interactions with the Eight Guardians—including figures like Minamoto no Yoshitsune (Kurō), Hinoe, and Taira no Atsumori—involve forging alliances, navigating trust, and influencing loyalties through her actions.

Facing new challenges in the sequel *Unmei no Labyrinth*, she contends with memory loss and a magical labyrinth threatening both worlds. Her commitment to restoring balance demands rebuilding bonds and confronting adversaries like the Heike's supernatural forces, highlighting her growth into a proactive guardian balancing personal desires with her duties as priestess. Her choices, particularly between staying with the Genji or siding with Masaomi, underscore themes of sacrifice and loyalty.