Uru Harune is the younger twin sister of Aira and Itsuki Harune, sharing an identical appearance with her twin Eru Harune. Both possess vivid red hair and eyes, styled in short side-tails. Uru’s ponytail rests on her left, while Eru’s falls on the right, distinguishing them clearly. Uru typically chooses yellow attire, contrasting Eru’s preference for orange. The twins attend Aira’s former preschool and initially help conceal Aira’s Prism Star activities from their father.

Adoring their older sister, Uru and Eru relish watching Prism Shows, often cheering for Aira’s performances, yet they feel lonely when her busy schedule keeps her away. During Aurora Dream, they make a pivotal appearance on their birthday, asking Aira, Mion Takamine, and Rizumu Amamiya to play. Aira takes them to Prismland, but sensing her reluctance, they flee in tears to hide in the Dream Tree. There, they encounter Kaname Amamiya. After Aira finds them, they express anger, claiming to hate her and Prism Shows, but forgive her when she apologizes and promises more time together. Kaname rescues them from a near fall, and Aira’s Pretty Remake cleans their dresses, reviving their joy. Witnessing Aira’s subsequent Prism Show inspires their future dream of becoming Pretty Top managers.

Uru’s family consists of father Hiroshi Harune and older siblings Aira and Itsuki. Her given name "Uru" means "sell" in Hiragana, while her surname "Harune" merges "spring" (春) and "sound" (音), signifying "sound of spring."