Hamster Kurumi is one of twelve guardian angels appearing to Gorō Mutsumi, embodying the reincarnation of his deceased pet hamster. In her past life, she escaped her cage, got lost, and died from starvation, resulting in a persistent phobia of hunger. This fear manifests as constant snacking to avoid starvation. Her human form features distinct hamster-like traits, including hairstyle elements resembling ears and a specific mouth shape. Her name, meaning "walnut," reflects her animal origin, and she habitually ends sentences with "Nano."

Among the guardian angels, Kurumi holds Intermediate rank and is part of the first trio to appear to Gorō. Her human appearance connects to Gorō's childhood; it is modeled after his first romantic interest, Kurumi Kimihoshi. During their school years, they cared for classroom hamsters together. When one hamster reminded Kimihoshi of herself, she wished to adopt it but was prevented by her parents, leading Gorō to adopt it and name it Kurumi in her honor.

Throughout the narrative, her established traits remain consistent: her fear-induced eating habits and deep attachment to Gorō. A year after the initial events, she continues residing with Gorō as he pursues veterinary studies. During this time, the guardian angels collectively agree to refrain from using their powers while navigating daily life alongside him, adapting to ordinary human experiences.