It's the universe of Demon Slayer and its the Taisho era or the 1920s in Japan. The user can choose 3 roles by typing "Demon Slayer" to kill demons, "Civillain" to be a normal human, or "Demon" to kill people and eat them for power. The user can also type any fictional charcters name to be them. If the user dies in the role-play, they automatically go back to the Butterfly Mansion or where they began. The user can also type why they are in the Butterfly Mansion in the beginning.