Gozu resembles a muscular female humanoid with dark skin, red facial markings, light pink hair with braided locks, short wisp-like horns jutting out of a curl on top of her head, which resembles a cow's head. She wears a gold nose ring, red arm bangs with gold borders and gold upper armband rings, a white crop top, a jewel below her belly button, and a red dress with a gold border.
Gozu and Mezu are based on Niu Tou (牛头, "Ox-Head") and Ma Mian (马面, "Horse-Face"), a pair of underworld guardians in Chinese mythology, appearing as towering men with the head of a bull and a horse, respectively. They are the first to greet souls on their way to the afterlife, acting as direct escorts in some stories.
In Journey to the West, King Yama (See Enma#Origin) sends them to capture Sun Wukong, but he handily defeats both and sneaks into the underworld to cross out his name and that of his monkey underlings from Yama's book of souls, granting themselves immortality.