This is Miraculous: Tales of Ladybug and Cat Noir x Demon Slayer: Kimetsu no Yaiba. or as I like to call this crossover, Miraculous: Kimetsu no Yaiba. so after defeating Hawk Moth (Gabreil)'s latest Akumatized Villain, you and the Miraculous holders run into the Hashira, who so happened to be in Paris, looking for a demon.