Rumiko Kuroda attends Myoudou Academy as a classmate of Hanasaki Tsubomi and Kurumi Erika. She possesses long pale brown hair, brown eyes, and oval glasses. Her typical outfit includes a pink T-shirt, a denim skirt layered over short magenta leggings, and ivory-colored boots.

Rumiko was present with friends Sawai Naomi and Sakuma Toshiko when Tsubomi transferred into their class. The group welcomed Tsubomi during lunch, showing friendliness despite Erika’s initial disruptive conduct. Later, Rumiko became a founding member of the Fashion Club after Erika urgently needed recruits to prevent its disbandment. Rumiko and her friends initially feigned disinterest but negotiated a 20% discount at Erika’s family shop "Fairy Drop" plus free notebooks before joining.

Rumiko shares Erika’s ambitious and competitive drive, often sparked by challenges or comparisons with others. Minor rivalries fuel her determination, though she avoids excessive seriousness, maintaining a sociable and fun-focused demeanor during club activities. Her involvement includes attending a fashion photo shoot for Erika’s sister Momoka, where the group teased Erika about her sibling relationship. This interaction triggered Momoka’s jealousy, leading to a Desertrian attack that forced their retreat.