A girl rescues what she thinks is a stray cat. The cat is actually a shapeshifting host to tiny supernatural creatures, and the moment she names him, he becomes real in ways that matter. What starts as a slice-of-life comfort story about adoption turns into a quiet supernatural war where the stakes are whether this new family gets to stay together, and every episode forces you to choose: is Xiaohei a pet, a person, or something else entirely that doesn't have a word in human language. The animation shifts between painterly softness and sudden violence without warning. It costs your certainty about what you're watching, and it's worth every second.

On a rainy night, a young girl named Luo Xiaobai rescues a stray black cat and brings him home. She calls him Luo Xiaohei. Xiaohei isn't just any cat: he is unusually clever, and he is a supernatural being who carries tiny creatures called Heixiu. His quiet new life soon comes under threat from a mysterious figure named Diting, who commands three winged wolves and sends them after Xiaohei. When Xiaobai takes him to the countryside to visit her cousin A Gen and her grandfather, a run of strange and fantastical events begins. The series mixes everyday comedy and slice-of-life moments with supernatural action and adventure.