Shiori Yumeoji, a third-year junior high student at Siegfeld Institute of Music, holds the prestigious title of "Frau Jade" as one of the school's Edels. She is deeply troubled by the unexplained departure of her older sister, Fumi Yumeoji, who transferred to Rinmeikan Girls School. Fumi provided constant care during Shiori's childhood struggles with chronic frailty, which limited her participation in activities and fostered her love for theater. The sisters promised to perform "Elysion" together at Siegfeld, with Fumi as Frau Platin and Shiori as Frau Saphir. This shared dream motivated Shiori to enroll at Siegfeld despite her health challenges, which she overcame through persistent effort. Following Fumi's departure, Shiori dedicated herself to excelling as an Edel to uphold their promise alone.

Petite with curly blonde hair and aqua eyes, Shiori wears Siegfeld’s uniform: a beige jacket, purple sweater vest, and dark pleated skirt. Her revue costume consists of a black collared jacket with gold trim, white skirt, combat boots, and a distinctive white-and-green cape. Her weapon is the curved saber "Jade Angriff."

Shiori exhibits a reserved and timid demeanor around strangers but transforms into an intense performer when angered or inspired. She values hard work, loyalty, and responsibility, often overexerting herself to meet Siegfeld’s standards. Her peers describe her as having self-sacrificing tendencies, intelligence, and a tendency to overanalyze situations. She struggles with insecurity when asked for advice due to her relative inexperience but remains deeply committed to personal and artistic growth.

Her relationships center on her unresolved bond with Fumi, whom she idolizes yet resents for abandoning their dream. Shiori initially felt overshadowed by Fumi’s legacy, desiring recognition for her own merits. They eventually reconnect during school events, culminating in Fumi expressing pride in Shiori’s performances. At Siegfeld, Shiori is mentored by Akira Yukishiro, who recognizes her potential to become Frau Platin and prevents her from overworking. She shares a warm friendship with Michiru Otori, who provides acting guidance and emotional support, and learns sewing from Yachiyo Tsuruhime.

Shiori excels in horseback riding and music, having learned piano and organ from her mother. She enjoys black tea and chiffon cake but dislikes natto. Her revue performances often metaphorically address her emotional journey, beginning with her debut: "The flower bud unfolds to show the path of platinum. The letter drenched in tears. Secretly depart on the jade road of dreams." Later revues symbolize her growth, including one where she and Fumi perform together as "sisters standing side by side on the dream stage."