Fuku

Fuku is a Fukuneko, a cat with powers that allow her to make the human of her choice happy. She was the cat of Umi, Ako's great-grandmother. After Umi's death, she became Ako's Fukuneko.

She used to call her former mistress "Mimi." She does the same for Ako because they resemble her. But Fuku eventually accepts Umi's death and finally calls Ako by her first name.

Fuku is said to be the first to have benefited from the powers of the cat god, making her a cat of noble lineage. She doesn't speak human language very well.

(Source: Nautiljon)