Juna Doma is a 19-year-old descendant of the legendary Lorelei, recognized by her blue hair and striking singing voice. She initially served as a commissioned officer in the Elfrieden Kingdom's Navy. Following the navy's dissolution, she was reassigned to the capital, where her grandmother, Duchess Excel Walter, tasked her with spying on the new king, Kazuya Souma, to evaluate his worthiness of support.

Juna became one of five individuals recruited during Souma's nationwide talent search. She assumed the role of "Prima Lorelei," the central figure in the kingdom's entertainment programming for Souma's Royal Voice Broadcasts. Using her voice to bolster public morale and disseminate information, she significantly contributed to the kingdom's cultural outreach. Close collaboration during these initiatives fostered genuine affection for Souma. With Excel's endorsement, she entered a romantic relationship with him, becoming his third fiancée. Their betrothal remained confidential initially to prevent public unrest due to her prominence as the Lorelei, requiring a smooth transition before a formal announcement.

Her background includes strong maritime traditions, reflected in her alias "Lady Canaria" within the Elfrieden Navy's Marine force, underscoring her family's influence in naval affairs through Excel. Juna adopts a pragmatic approach, emphasizing realism in decision-making. Her composed demeanor and analytical skills positioned her as a trusted advisor within Souma's inner circle, influencing both cultural and strategic initiatives.

Among Souma's brides, Juna assumes an "oneesan" (elder sister) role, providing stability and guidance. Her journey illustrates a shift from a spy motivated by familial duty to a loyal consort dedicated to the kingdom's prosperity. Her integration into the royal family exemplifies her adaptability and commitment to supporting Souma's vision.