Yumi is a shy human girl with a deep aspiration to become an idol singer. She possesses fair skin, long brown hair usually braided during events (though unbraided by the story's end), and distinctive dark blue eyes.

A close childhood friendship with Hikari, who moved away, profoundly scarred Yumi. This departure transformed her from a cheerful, self-assured girl, especially about her singing, into someone distant and lacking confidence. Before leaving, Hikari gifted Yumi a handcrafted doll. This doll becomes Yumi's crucial emotional anchor, directly inspiring the design of the Hannari Komachi dress.

Yumi battles persistent self-doubt, notably during her Sweet Records audition where timidity cripples her performance. Magical protagonists cross her path, initially failing to lift her spirits with their abilities. After an emotional confrontation and reconciliation among themselves, they assist Yumi by coordinating her audition outfit: the Sweeping Style hairstyle, Hannari Komachi dress, and Tri-Ribbon Boots.

Seeing herself in the Hannari Komachi dress triggers a pivotal realization for Yumi – its design visually echoes Hikari's handmade doll. This connection reignites her determination, enabling her to overcome her fears. She performs "Angel" and "Re-Born" with renewed confidence, winning the audition. Following her victory, she reconnects with Hikari and navigates a blossoming bond with her supportive friend Shou.