The world of 'Demon Slayer' is packed with supernatural creatures, but true 'demon animals' aren't a major focus. Most demons are former humans transformed by Muzan's blood, though some have animalistic traits—like the Lower Moon Rui's spider family or the serpentine Hantengu clones. Even the Upper Moon demons blend human and beast features; Akaza's markings resemble a tiger's stripes, while Kokushibo's multiple eyes feel insect-like. The series leans more into yokai-inspired designs than literal animals, which makes sense given its Taisho-era folklore roots. I'd love to see a spin-off exploring actual demonic creatures, though—imagine a crow infused with Muzan's blood causing havoc!
That said, the manga does feature animals with supernatural ties, like Tanjiro's loyal crow messenger or the mystical Blue Spider Lily foxes mentioned in lore. They're not 'demons' per se but exist in that blurred space between spirit and beast. It's interesting how the series avoids typical werewolf or vampire tropes, instead crafting its own mythology where humanity's corruption creates monstrosities. The closest we get to demon animals might be the mutated biwa-playing demon in the Infinity Castle arc—her fusion with the instrument feels almost like a cursed object possessed by a beast's spirit.