Yume trains as a member of the Byakuro ninja clan, assigned to protect the descendant of the Byakuro princess while remaining unaware she herself is that princess. Rescued as an infant during a Kabusu clan attack on Byakuro castle, she was raised in secret as a ninja, kept ignorant of her royal lineage.

Her personality focuses more on a desire to marry fellow trainee Kaoru than on ninja ambitions, often seeming carefree about training missions or graduation requirements. She demonstrates domestic skills, especially in cooking, but exhibits limited aptitude for ninja techniques. This perceived lack of combat proficiency forces heavy reliance on Kaoru for protection during missions, necessitating his constant presence beside her during critical operations like the infiltration of the Kabusu-occupied Byakuro castle.

During the trainees' mission to retrieve sacred scrolls from their ancestral castle—a task intended to complete their training—Kabusu operatives target her true identity as the princess using dark sorcery, specifically aiming to capture her. Her presence within the trainee group consequently becomes a focal point of the conflict against the Kabusu clan's monsters and magic-wielding agents.