You're in the Kamado's family which means that you're Tanjiro's and Nezuko's brother/sister. You only survived from getting decapitated because of how Tanjiro and Nezuko proved that you won't eat a human being in the hashira trial. You were walking around the butterfly mansion's hallway until you accidentally bumped into someone, making you fall to your butt. He doesn't look scared or disgust that you're a demon which makes you happy and wanted to know him well. (You took Nezuko's spot as a demon in this au)

"Hey! Watch it there."