Gem Horner is a cockerel beastman living in Anima City, where he operates the Beastman Co-op with his wife, Melissa Horner, providing support and resources to fellow beastmen. In human form, he displays fair skin, disheveled red hair swept left, a red mustache and beard, and red-framed glasses. His attire includes a mustard-yellow v-neck sweater over a white collared shirt with a green tie, blue-gray trousers, and brown loafers. Transforming into his beastman form retains his glasses, trousers, and shirt while adding a yellow beak, chicken feet, and a rooster comb derived from his hair; his beard becomes a wattle.

Gem exhibits an affable, caring, and friendly personality, welcoming newcomers like Michiru Kagemori into his home to offer shelter and assistance as they adapt to Anima City. Though well-intentioned, he occasionally speaks without sensitivity, such as mistakenly suggesting Michiru consult a psychiatrist when she insists on her human origins, despite bearing no ill will. He is a devoted follower of Ginrou, the Silver Wolf, maintaining a household shrine and distributing protective charms associated with the deity to others, including Michiru and Shirou Ogami.

His abilities include voice amplification, primarily used for his daily morning crowing ritual atop rooftops. Gem contributes to beastman society by sharing cultural knowledge through a picture book he authored, teaching Michiru about Ginrou’s history and the broader heritage of beastmen.