Rumy is an infant girl of the "Elves to the Sorcerers" tribe. She wields limited magical abilities, casting weak spells like "Fire," "Cold," "Stop," and "Fly"—powers rarely deemed effective or useful by her adventuring companions. Her physical traits include striking silver hair and violet eyes.

She shares an inseparable bond with Shiro, a white dragon who frequently masquerades as a puppy. Rumy is consistently portrayed clinging to or accompanying Shiro, underscoring their profound attachment. Within the adventuring group, she embodies the role of the "childish one."

Rumy actively joins quests with core characters, including expeditions tied to mysterious jewels. For instance, she accompanies Clay, Pastel, and Shiro to investigate twin white dragon jewels, journeying to Mount Terrason to probe potential connections to Shiro's origins. Her contributions in these adventures consistently reflect both her modest magical skills and her deep reliance on Shiro.