Kurumi began as human Kurumi Kimihoshi, born August 6, 1975. She became Goro Mutsumi's childhood friend and first love during middle school, where they served together as classroom monitors caring for pet hamsters. When the hamsters multiplied, Kurumi developed a strong attachment to one female hamster resembling herself, naming it Morilin. Unable to adopt Morilin due to parental disapproval, she became visibly distressed. Aware of her feelings, Goro adopted the hamster. Though intending to keep the name Morilin, Kurumi insisted he change it; he chose "Kurumi" after his first love, symbolizing his affection for her.

Born as a hamster under Goro's care on July 4, 1988, this Kurumi learned to escape her cage and became lost. Discovered by Goro after three days missing, she had died from starvation. This traumatic experience profoundly influenced her reincarnated form, instilling a deep-seated fear of starvation.

Reincarnated as a guardian angel, Kurumi retained the name and appearance of Goro's human childhood friend. She manifested as one of twelve guardian angels protecting Goro, holding an Intermediate rank. Her personality is carefree, marked by constant snacking due to her fear of hunger. She frequently uses the phrase "Nano" in her speech. Her physical design incorporates elements reminiscent of a hamster, including her hairstyle and facial features.

Her relationships with other guardian angels are significant. She shares a close friendship with Ran and maintains a generally amicable bond with Tsubasa, though they occasionally argue. Initially, Kurumi and Tamami exhibited intense hostility, frequently clashing and attempting to undermine each other, but their relationship evolved into a close friendship. Kurumi adores Goro and demonstrates unwavering loyalty, though her excessive eating habits often strain his finances. Her yellow image color and association with hamsters remain consistent traits.