Kuaru is a hybrid being blending human and big cat features, designated as one of three goddesses guarding the Tower of Babel. She uniquely bears permanent prominent animal traits: long ears, a tail, and distinctive fangs. Initially presented as a "souvenir" gift from Mutsuki to Kanzaki, she was characterized as affectionate toward humans, well-trained, and embodying the ideal pet.

Her early existence lacked personal history; she arrived nameless and unaware of her origins. Her initial existence centered solely on serving her master through sensual acts. This changed after her first sexual encounter with Kanzaki, who then bestowed her name. Beyond her hybrid form, Kuaru possesses the physical capability to fully transform into a big cat, gaining near-total fur coverage and superhuman strength.

Her narrative role is intrinsically tied to Kanzaki's identity as the reincarnated King of Atlantis. Functioning as a "magical sex servant," she engages in erotic trials and adventures to aid him in regaining his former power and reclaiming his lost kingdom. Their relationship evolved beyond servitude, resulting in the birth of over a dozen children.