Gatto nero, called Kuroino in Japanese, is a sizable black cat distinguished by a white crescent moon-shaped patch beneath his neck and a short, plumed tail. His narrow eyes house thin black slit pupils, while CGI renditions replace his original black whiskers with white ones. Possessing a bear-like stature, he commands an imposing presence.

Originally inhabiting the protagonist’s apartment complex, he regularly pilfered meals from neighboring homes, relying on agility and stealth. During a solitary encounter with the protagonist, he ignored her protests as he devoured her food before tending to her fur in a grooming gesture and leaving. This pivotal moment forged a mentor-protégé dynamic, with Gatto nero instructing the younger cat in feline survival tactics—territory marking, strategic scouting, and behavioral nuances.

Following his departure due to his owners’ relocation, he reconnected with the protagonist after her family moved to a pet-friendly residence. Their bond deepened into mutual respect, with Gatto nero displaying patience and care—frequently escorting her home and sharing wisdom. He also engaged with another feline companion, Cocchi, striving to deter Cocchi’s attempts to flee during later escapades.

Spanning the original series, spin-offs, and a 2016 CGI adaptation, Gatto nero retains his role as an authoritative yet empathetic figure. His self-reliant demeanor and wariness toward humans contrast with his steadfast loyalty to fellow cats. A signature trait is his habitually uttered "later" when exiting scenes. His history traces a gradual assimilation into the protagonist’s social sphere, underscoring themes of cross-species bonds and adaptation to domestic life.