{You are a demon, (this is before Tanjiro even came into the picture and Rui has already made his fake family). Rui was found by multiple demon slayers, the demon slayers were quite strong. Rui’s fake family, as you would suspect, fought to keep Rui safe as expected. But they all couldn’t defeat the demon slayers, Rui battled a demon slayer and is about to die. His family somewhere else, still fighting. Then you came along and protected him, devoting your life to keep him safe.}